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View Full Version : When would I manually shift gears with my automatic transmission?


Nars Glinley
07-19-2012, 09:11 AM
Like most (all?) people, I put my car in "D" and go about my driving business. But next to the big D, there's a "3 2 1". Are there any good situations to use them? I can kind of (maybe) see the usefulness of first gear but the other two just seem completely unnecessary.

mecaenas
07-19-2012, 09:15 AM
When going downhill for an extended period of time you can put the car into a lower gear to slow you down so you don't ride the brakes.

Alka Seltzer
07-19-2012, 09:15 AM
One situation where you might want to lock the car in a particular gear is driving in icy conditions. You don't want the car changing down while going around a sharp corner, as the increase in torque can cause the wheels to break traction. This actually happened to my driving instructor once, it changed down to first and he had a very slow speed collision with a hedge.

MacdaddyC
07-19-2012, 09:46 AM
I use my 3 gear to while towing. Using D can burn out your overdrive.

jz78817
07-19-2012, 10:00 AM
I use my 3 gear to while towing. Using D can burn out your overdrive.

while that may have been the case in the early days of 4-speed transmissions, the reason nowadays is because overdrive can drop the engine too low in its powerband for towing anything effectively.

Nars Glinley
07-19-2012, 10:11 AM
I use my 3 gear to while towing. Using D can burn out your overdrive.

My Chevy truck has a towing mode button on the gear shift although I don't think I've ever used it. How is that different than putting it in 3?

Mdcastle
07-19-2012, 10:14 AM
When driving in hilly areas I tend to manually downshift one gear since it's easier to maintain a constant speed. As already noted it provides engine breaking going downhill. Going uphill the car would eventually downshift itself, but usually loses speed first before it reacts. This is the most common scenerio, going from Overdrive (4) to (3), so often there's a button you can just push to save you the trouble of moving a big lever...

(2) and (1) are generally less useful, except for for some situations off-roading in a 4wd vehicle, (Though I could maybe see (2) for engine braking on *very* steep roads). My Jeep Grand Cherokee has them being off-road capable but some vehicles omit them (like my sisters Toyota Corolla).

In addition 4 wheel drive vehicles have a shifter for the transfer case, for my full time 4WD its [Hi] for normal driving [Neutral] to disengage for being towed, and [Lo] for when you need a lot of power as opposed to speed, say extreme off-roading or pulling a boat out of a lake.

Machine Elf
07-19-2012, 10:15 AM
Back in the '80's and '90's, my dad took us on summer vacations to the western US in a station wagon towing a pop-up camper. Some of these station wagons (he went through several over the decades) had overdrive on them. In cruise control on a level highway everything was fine, the transmission stayed in top gear. But if we came to a significant hill, the speed dropped and the cruise control put the throttle down enough to make the transmission downshift. With the extra torque at the wheels, the speed climbed back up, the cruise control eased up on the throttle, and the transmission upshifted - and then the decel-downshift-accel-upshift cycle would repeat until we crested the hill. The solution was to wait until the first automatic downshift as the climb began, and then move the PRND321 selector down a notch to hold it in that lower gear until cresting the hill. For even slower ascents on very steep mountain grades, you could just as easily select a lower gear - 1 or 2, depending on the grade and twistiness of the road. If you've never been to the mountainous areas of the western US - especially away from major interstate highways - the roads can be graded pretty steeply, and there are often switchbacks and squiggles that necessitate a very low speed.

If we were going to descend a long mountain grade, letting the transmission stay in overdrive would allow the whole rig to build up a lot of speed, requiring heavy braking to keep it within reason. Solution: when cresting the grade, if a long, steep descent was awaiting us, we'd leave the PRNDL321 selector in the lower position that we had chosen for the climb. You still needed some braking, but not nearly as much as if the transmission were in top gear.

Most small, lightweight cars won't be towing much of anything, but if they've got a low power-to-weight ratio and/or if they're carrying a full load of people and cargo, they'll still struggle to climb mountain roads. Not only are those roads steep as described, but you're also at high altitude, typically above 5,000 feet in the Rockies, and the thin air up there robs the engine of a significant fraction of its output. So even though you're not dragging a trailer behind you, you may still want to force a lower gear to prevent the transmission from constantly upshifting-downshifting-upshifting-downshifting.

Kevbo
07-19-2012, 04:32 PM
Exactly what Machine Elf said. Flatlanders just don't get that you can have several miles of 7% grade, followed by a mile or so of 9%. Brakes are sized and designed to provide several full speed stops. They are not sized to control speed down multiple miles of mountain grade.

Lemur866
07-19-2012, 04:42 PM
I've also used 1 and 2 for very slow driving in terrible ice/snow/slush conditions, where I wanted to drive 5 miles per hour without having to ride the brake.

pulykamell
07-19-2012, 05:08 PM
I've also used 1 and 2 for very slow driving in terrible ice/snow/slush conditions, where I wanted to drive 5 miles per hour without having to ride the brake.

I've always wondered how this works.

I drive a stick. When I'm in really slick or snowy conditions, I may start from a standstill in 2nd gear instead of first, so as not to be as likely to spin my tires. Now, in an auto "1" and "2" will limit the gear selection to first gear, and to first and second gear, respectively, right? When you're driving 5 miles per hour, why would an auto be outside of 1st gear? "2" doesn't mean second gear, does it? It means first and second, no? So when you're at 5 mph, why would you be riding the brakes? Surely, the auto isn't past first gear at that speed, is it? At worst, I guess it might be on second, but I personally can't remember any autos I've driven where 5 mph would be anything but first gear.

Skammer
07-19-2012, 05:23 PM
Sometimes my car won't start out in first gear when the transmission is in D. I have to manually shift into first, get up to speed, then shift to D.

I realize that's a problem with my car somewhere and not a normal thing.

Encinitas
07-19-2012, 05:24 PM
If your brakes go out, you can gradually downshift to lessen your speed (somewhat) before you crash into something.

Lemur866
07-19-2012, 05:27 PM
All I know is if you have your foot off the gas in D you go forward faster than you do when you have your foot off the gas in 1.

pulykamell
07-19-2012, 05:50 PM
All I know is if you have your foot off the gas in D you go forward faster than you do when you have your foot off the gas in 1.

This is interesting. Why would this be the case? I've personally never noticed this in my autos, but the last time I owned an auto was 20 years ago, so maybe things have changed.

pete66
07-19-2012, 06:02 PM
My Chevy truck has a towing mode button on the gear shift although I don't think I've ever used it. How is that different than putting it in 3?Tow/Haul mode doesn't keep you out of overdrive. It just adjusts when the transmission shifts. Usually it will delay the shift when climbing a grade to allow higher rpms before shifting, and shift earlier allowing more drag from the engine and transmission when descending. At least that appears to be what my dodge does.

kanicbird
07-19-2012, 06:49 PM
In some cars '2' will stay in 2 and not vary between 1 and 2. This allows you to start driving in second instead of first, useful on slippery conditions where 1 would spin the wheels.

Simple Linctus
07-19-2012, 07:07 PM
Like most (all?) people, I put my car in "D" and go about my driving business. But next to the big D, there's a "3 2 1". Are there any good situations to use them? I can kind of (maybe) see the usefulness of first gear but the other two just seem completely unnecessary.

Not to be rude, but if you're asking this question then in a sense the answer is no - there are no good situations where you would use them.

There are umpteen reasons why a good driver would want to use them. These can be broken down into either car handling reasons where you would not want the car to suddenly upshift (or downshift if it were in a higher gear) (which in the worst cases could cause an instant spin if the car were near the limit of adhesion) or roadcraft reasons where as a driver more intelligent than the gearbox you either want the engine in a different part of its powerband (e.g. you anticipate overtaking someone soon, which if you're doing it properly you don't want to be just relying on kickdown) or you want increased engine braking (such as the hills example). If your gearbox is crap then there is a reason 2.5, you want to stop it from hunting.

If you are interested in being a good road driver, although it is a British book it is still the one to start with - Roadcraft: The Police Driver's Handbook (http://amazon.co.uk/Roadcraft-The-Police-Drivers-Handbook/dp/0113408587). It teaches a system to use in all aspects of driving that is the foundation of pretty much all advanced driving groups I am aware of.

pulykamell
07-19-2012, 07:56 PM
In some cars '2' will stay in 2 and not vary between 1 and 2. This allows you to start driving in second instead of first, useful on slippery conditions where 1 would spin the wheels.

That's interesting. The automatics I've had didn't work this way, but that would make sense to start in 2 in slippery conditions if the transmission locks into second gear and skips over first. What doesn't make sense is why "D" would accelerate faster than "1" with the foot off the brake, as in Lemur's case. Wouldn't both transmissions be in first in that case? Why would riding the brake in "D" cause the car to go faster than riding it in "1"? I could believe it's some quirk of autos, but I'd be interested in hearing what's going on to make this the case.

Nars Glinley
07-19-2012, 08:00 PM
Not to be rude, but if you're asking this question then in a sense the answer is no - there are no good situations where you would use them.

Not into the whole fighting ignorance thing, are you?

Mdcastle
07-19-2012, 10:20 PM
Also I've noticed a number of people haven't the foggiest idea what a tach is, and how it can be useful if you manually shift gears.

GameHat
07-19-2012, 10:42 PM
Manual transmission guy speaking here: I drive a 5-speed 2007 Mustang GT. Nice little entry-level "performance" car.

Typically, you want the lower gears for either speed limiting (going downhill without wearing out your brakes) or for passing. I'll discuss snowy driving as well (I live and drive in the upper midwest, where snow, ice and sleet are common in winter months.)

If you have a long downhill stretch (mountains) it may be better to keep the car in a low gear (probably 2nd) to ease the load on your brakes. This is more applicable for semi trucks - they're huge, heavy, and they can absolutely ruin their brakes and lose control if they don't downshift on long hills. But most cars can handle the braking necessary on long downhill stretches, unless you're doing it every day, repeatedly. But it is helpful. I do have one steep hill in my normal driving area; when I'm going down it it's nice to just put the car in 2nd to have more speed control and not have to stand on the brake pedal.

3rd gear on most cars is a good "passing" gear - meaning, you're on the highway, you want to pass someone. 3rd gear is good for getting reasonably quick acceleration without putting your tach into the redline. I do this all the time. The difference here between manual and auto trannys is that in all the autos I've driven, you shift to the left (passing) lane, floor it, and whatever controls the auto takes a few seconds to realize you really want to go fast. In a manual, you just shift and go.

As for snow/ice - and I say this driving a RWD Mustang near Chicago (So I am familiar with driving in snow with a car totally unsuited for such a thing):

If you get stuck on a slippery area, having control of the gear is very helpful. An earlier poster suggested that 2nd is the gear you want; I disagree, at least for my vehicle. What you really need to do to get moving on snow or ice is first: Disable traction control. Traction control kills power to the wheels if it senses that they're slipping. Traction control is a great safety feature when the car is in motion; it's terrible for getting the car moving.

Personally, I've had the best luck putting it in 1st with traction control off, and giving it a good amount of throttle. Often you end up going forward a bit, then losing traction and spinning the wheels. Then you want to put it in reverse, and again, give it a good amount of throttle. I usually end up rocking back and forth a bit, but I've never gotten stuck. Just keep rocking back and forth until you get the momentum to keep going.

Once you're moving on snow and ice, absolutely turn traction control back on. It really is a good safety feature, it just makes it harder to get started.

pulykamell
07-19-2012, 10:59 PM
=

If you get stuck on a slippery area, having control of the gear is very helpful. An earlier poster suggested that 2nd is the gear you want; I disagree, at least for my vehicle. What you really need to do to get moving on snow or ice is first: Disable traction control. Traction control kills power to the wheels if it senses that they're slipping. Traction control is a great safety feature when the car is in motion; it's terrible for getting the car moving.


Traction control? Fancy pants car. :)

For the vehicles I've had, in slippery situations, both snow and rain, personally, I've found it easier to start from second, as it's really easy to spin the tires in first. I generally try not to do the rocking-back-and-forth action, as it tends to make a bad situation worse. I try to slowly ease out and get traction, if I can. Admittedly, sometimes, you just gotta rock it. If you look it up, starting in a higher gear for slippery situations is fairly standard advice. YMMV.

Looking it up, it does seem that in a lot of automatics these days, 2 means "second gear only" and not "first and second." I could swear my in my 80s and 90s era automatics, "2" meant limiting the gears to first and second, but perhaps I was not as observant back then as I am now, as I didn't drive sticks until the late 90s.

Kenm
07-19-2012, 11:59 PM
In some cars '2' will stay in 2 and not vary between 1 and 2. This allows you to start driving in second instead of first, useful on slippery conditions where 1 would spin the wheels.Years ago, this was the case with Fords and was very handy in snow or on ice. But it was not the case with GMs or Chryslers, and isn't now. I don't know whether Ford stuck with it.

AaronX
07-20-2012, 02:39 AM
One situation where you might want to lock the car in a particular gear is driving in icy conditions. You don't want the car changing down while going around a sharp corner, as the increase in torque can cause the wheels to break traction. This actually happened to my driving instructor once, it changed down to first and he had a very slow speed collision with a hedge.

To my knowledge, gear "2" on automatics means the max gear the transmission will choose is 2, it may also choose 1. To those people who say it will only choose 2 - can you get your car to shudder/stall on 2? Or, launch the car in 1 and immediately shift to 3. Does the car change gears when you shift?

So, as people have said, it limits the gears your transmission will choose, for:
1. more power (climbing)
2. engine braking (downhill), also if your brakes don't work
3. traction
Something nobody has mentioned: if you want the fastest acceleration, you should stay in lower gears longer before shifting, but cars normally don't do that because it wastes fuel. So you can "manually" upshift using the gears on an automatic to accelerate faster.

The interesting thing is - what was the main reason to have those gears on automatics - performance or safety? If engine braking required higher gears, would automatic transmissions limit the MINIMUM gear, or still the maximum?

bengangmo
07-20-2012, 03:26 AM
To my knowledge, gear "2" on automatics means the max gear the transmission will choose is 2, it may also choose 1. To those people who say it will only choose 2 - can you get your car to shudder/stall on 2? Or, launch the car in 1 and immediately shift to 3. Does the car change gears when you shift?

So, as people have said, it limits the gears your transmission will choose, for:
1. more power (climbing)
2. engine braking (downhill), also if your brakes don't work
3. traction
Something nobody has mentioned: if you want the fastest acceleration, you should stay in lower gears longer before shifting, but cars normally don't do that because it wastes fuel. So you can "manually" upshift using the gears on an automatic to accelerate faster.

The interesting thing is - what was the main reason to have those gears on automatics - performance or safety? If engine braking required higher gears, would automatic transmissions limit the MINIMUM gear, or still the maximum?
Cars are continually getting better and more intelligent with their shifting patterns. I know some brands that have a "snow" setting for the auto, that will start it in second.
On top of this, the way that an automatic works is inherently more gentle than a manual.

But I would also need to point out, in my auto if I mash it for max acceleration, the car will hold the gear until redline before shifting - so the short shifting you are referring to may not neccessarily be true.

Alka Seltzer
07-20-2012, 05:27 AM
To my knowledge, gear "2" on automatics means the max gear the transmission will choose is 2, it may also choose 1. To those people who say it will only choose 2 - can you get your car to shudder/stall on 2? Or, launch the car in 1 and immediately shift to 3. Does the car change gears when you shift?

I think you'd need to check the manual of the particular car to be sure. From the wiki article (http://en.wikipedia.org/wiki/Automatic_transmission):

Second (2 or S)
This mode limits the transmission to the first two gear ratios, or locks the transmission in second gear on Ford, Kia, and Honda models.

AaronX
07-20-2012, 07:05 AM
Ok the instructions for the 2011 Honda Accord say 2 locks the transmission, but D3 may select lower gears. 2011 Toyota Camry says it'll select that and lower gears. I guess second gear is powerful enough to do without first.

Broomstick
07-20-2012, 07:22 AM
Surely, the auto isn't past first gear at that speed, is it? At worst, I guess it might be on second, but I personally can't remember any autos I've driven where 5 mph would be anything but first gear.
Automatics will roll forward in D without your foot on the accelerator, it's called "idle speed" or something of the sort. In many automatic cars that speed can be faster than 5 mph. In other words, you have to ride the brake in D to slow it down to 5 mph. Putting it into a lower gear gives it a lower idle speed and eliminates the need to ride the brake.

Why is it done that way? Haven't the foggiest notion, but I can always spot someone who's only driving experience is with manuals because they don't know about that quirk and/or are surprised by the car wanting to creep/roll forward in D without input from them.

pulykamell
07-20-2012, 07:44 AM
Automatics will roll forward in D without your foot on the accelerator, it's called "idle speed" or something of the sort. In many automatic cars that speed can be faster than 5 mph. In other words, you have to ride the brake in D to slow it down to 5 mph. Putting it into a lower gear gives it a lower idle speed and eliminates the need to ride the brake.

I do know about riding the brake in automatics. But wouldn't you be in first gear off the line whether you're in D or 1 on an automatic? This is what I'm wondering about. Plus, off the line, the lower gear should accelerate faster to 5 mph than the higher one, anyway, if D starts you off in anything but first. I guess I could see that if the auto switches to second by 5 mph, it should eventually coast faster, but is the shift point that low?

TonySinclair
07-20-2012, 07:53 AM
Typically, you want the lower gears for either speed limiting (going downhill without wearing out your brakes)

It's cheaper to get new brakes than a new engine. Is it definite that long downhill stretches of engine braking don't decrease the life of your engine?

Broomstick
07-20-2012, 08:07 AM
I do know about riding the brake in automatics. But wouldn't you be in first gear off the line whether you're in D or 1 on an automatic? This is what I'm wondering about. Plus, off the line, the lower gear should accelerate faster to 5 mph than the higher one, anyway, if D starts you off in anything but first. I guess I could see that if the auto switches to second by 5 mph, it should eventually coast faster, but is the shift point that low?
Honestly.... I don't know. My current car has a computer that, when it comes to driving matters, is smarter than I am. I don't know how it was programmed but these days either alternative is possible.

Richard Pearse
07-20-2012, 08:17 AM
It's cheaper to get new brakes than a new engine. Is it definite that long downhill stretches of engine braking don't decrease the life of your engine?

But you need to get new brakes while you own the car, a new engine will most likely be someone else's problem.

Rick
07-20-2012, 08:19 AM
It's cheaper to get new brakes than a new engine. Is it definite that long downhill stretches of engine braking don't decrease the life of your engine?
No it does not.

jz78817
07-20-2012, 09:02 AM
It's cheaper to get new brakes than a new engine. Is it definite that long downhill stretches of engine braking don't decrease the life of your engine?

No. "engine braking" means using the pumping losses of the engine trying to draw air through a closed throttle combined with a lower gear ratio to slow the car. It does not cause any additional wear in the engine of any consequence.

Nars Glinley
07-20-2012, 09:09 AM
It's cheaper to get new brakes than a new engine. Is it definite that long downhill stretches of engine braking don't decrease the life of your engine?

It won't be cheaper if your brake fluid boils and you can't stop when needed.

Machine Elf
07-20-2012, 09:35 AM
It's cheaper to get new brakes than a new engine. Is it definite that long downhill stretches of engine braking don't decrease the life of your engine?

Your engine is likely to last for a few thousand hours of run time. Over the life of your vehicle, deliberate engine braking is not likely to compose more than an hour of that time. Moreover, engine braking puts less load on the engine than highway cruise, and with lower temperatures (since little or no fuel is being burned in the combustion chambers. Wear due to engine braking will be negligible.

If you are descending a miles-long 9% mountain grade with a car full of meat and/or cargo, using the friction brakes to decelerate from 80 MPH down to 60 MPH three times per minute for a few minutes stands a fair chance of cooking your brakes. You may warp the rotors, you may experience reduced braking capacity due to brake fade (pad friction coefficient reduces at very high temperature) or in severe cases (especially with moisture-contaminated brake fluid) you may boil the brake fluid and lose braking ability altogether.

Descending a one-block-long hill in San Francisco at 20 MPH? Don't bother downshifting your automatic transmission; your friction brakes will do just fine here.

Something nobody has mentioned: if you want the fastest acceleration, you should stay in lower gears longer before shifting, but cars normally don't do that because it wastes fuel.

Automatic transmissions will shortshift if you're light on the throttle - but if you've got your foot to the floor, the computer will not shift until RPM's are at or near the redline; no need to use the selector to delay the shift.

All I know is if you have your foot off the gas in D you go forward faster than you do when you have your foot off the gas in 1.

If the transmission is not in neutral, the car wants to creep forward until the engine is idling at the same speed it would idle at in neutral*. If you let it upshift (i.e. the selector is in "2" or "D"), then once the car gets going fast enough, it will shift up to a higher gear and end up idling forward faster than if you had held it down in first gear. Listen/feel carefully (especially if you've got a tachometer on the display), and you can probably tell where the shift is.

*late-model vehicles may open the throttle slightly when you put the transmission in gear so as to avoid having the RPM's drop precipitously, so if you let it roll forward at its desired speed, the RPM may end up being higher than you would see if you were stopped with the selector in "P" or "N".

kanicbird
07-20-2012, 09:54 AM
To answer the question about cars that 2nd means 2nd only. There is no problem with the engine studdering, it appears the car is just as happy starting out from a stop in 2nd as 1st, though with less acceleration.

Also some automatic cars with a 'manumatic' mode, meaning you control the shifting of a automatic transmission by moving a shifter to up/downshift - autoshifting doesn't happen, allow the start from a stop in 2nd by using the manumatic mode. Subaru is one such manufacturer, at least some of their older models, where to start out in 2nd you would have to use the manumatic shifter to change from 1 to 2 at the stop, then you start out in 2.

pulykamell
07-20-2012, 10:52 AM
To answer the question about cars that 2nd means 2nd only. There is no problem with the engine studdering, it appears the car is just as happy starting out from a stop in 2nd as 1st, though with less acceleration.

Also some automatic cars with a 'manumatic' mode, meaning you control the shifting of a automatic transmission by moving a shifter to up/downshift - autoshifting doesn't happen, allow the start from a stop in 2nd by using the manumatic mode. Subaru is one such manufacturer, at least some of their older models, where to start out in 2nd you would have to use the manumatic shifter to change from 1 to 2 at the stop, then you start out in 2.

Hell, with some of the really torquey cars, you can even start in 3! (My friend's 2012 Camaro is a manumatic with paddle shifters, and I was surprised that it would let me select 3 to start in manual mode. But not 4. :) )

Kevbo
07-20-2012, 11:32 AM
It's cheaper to get new brakes than a new engine. Is it definite that long downhill stretches of engine braking don't decrease the life of your engine?

It is even more expensive to haul the remains of your car out of the ravine* and and embalm and bury your corpse after you boil your brake fluid and fail to make that last hard turn on a mountain grade. Yes, brakes are far better now than they used to be, assuming they are maintained. When was your brake fluid last replaced? How much lining do you have left on your pads? Are your brake hoses in good condition or are they getting spongy?

Engine braking lightly loads the back sides of gear teeth, and the opposite half of journal bearings that see very little wear otherwise. It is at fairly high RPM giving full oil pressure and low forces, so wear is virtually nil. Yes it adds some minute wear, but it is wear to areas that won't wear out anyway, and will still be fine long past the point where wear from normal driving requires replacement or rebuild of components. Many modern engine control units completely stop the flow of fuel under these conditions, so it can actually use less fuel than riding the brakes.

It is absolutely false to say that brakes were designed to control speed and transmissions/torque converters/clutches/etc. were not. The existence of options other than "D" betrays the fact that the designers envisioned valid uses of those selections.



*expensive enough that they often just leave the dead cars to rust away.

GameHat
07-20-2012, 10:31 PM
Traction control? Fancy pants car. :)

For the vehicles I've had, in slippery situations, both snow and rain, personally, I've found it easier to start from second, as it's really easy to spin the tires in first. I generally try not to do the rocking-back-and-forth action, as it tends to make a bad situation worse. I try to slowly ease out and get traction, if I can. Admittedly, sometimes, you just gotta rock it. If you look it up, starting in a higher gear for slippery situations is fairly standard advice. YMMV.

Looking it up, it does seem that in a lot of automatics these days, 2 means "second gear only" and not "first and second." I could swear my in my 80s and 90s era automatics, "2" meant limiting the gears to first and second, but perhaps I was not as observant back then as I am now, as I didn't drive sticks until the late 90s.

Hey, I'm just speaking from experience :D

I'm talking getting started in snow that has piled up to halfway the height of the tire.

Spinning the tires is almost always bad. You're just compressing the snow/ice into a slick nightmare. When I talk about rocking I mean move forward until the tires slip, quickly shift, move in reverse till the tires slip, back into 1st, repeat.

That said - In heavy snow/ice I've tried 2nd gear, and it just simply doesn't work (in my car). You really need to get momentum - I can get my car moving on dry asphalt in 2nd (or even 3rd, the few times I've made the mistake of thinking 3rd was 1st) but on an icy, slippery road - only 1st will do.

And yeah, I have traction control, but for getting the car going from a stop in icy conditions - it needs to be off.

:D

AaronX
07-21-2012, 01:50 AM
Automatic transmissions will shortshift if you're light on the throttle - but if you've got your foot to the floor, the computer will not shift until RPM's are at or near the redline; no need to use the selector to delay the shift.

Do you mean if I were to drag race an automatic car, all I have to do is floor the accelerator?

Richard Pearse
07-21-2012, 05:34 AM
Do you mean if I were to drag race an automatic car, all I have to do is floor the accelerator?
Yeah, if you want quick acceleration in an automatic, say if you want to overtake someone, floor the accelerator and it'll drop down a gear and shift at, or close to, the red line.

Satellite^Guy
07-23-2012, 12:44 AM
Hell, with some of the really torquey cars, you can even start in 3! (My friend's 2012 Camaro is a manumatic with paddle shifters, and I was surprised that it would let me select 3 to start in manual mode. But not 4. :) )

When I took driver training (in a manual), back in 1990, my instructor demonstrated that you can start a car in any gear, without using any throttle, by putting it in every gear, and gently letting up on the clutch, enough to get it rolling. He then got me to do it in 1st gear. I guess this teaches one to be gentle with the clutch, to eliminate jerky starts.

pulykamell
07-23-2012, 02:26 AM
When I took driver training (in a manual), back in 1990, my instructor demonstrated that you can start a car in any gear, without using any throttle, by putting it in every gear, and gently letting up on the clutch, enough to get it rolling. He then got me to do it in 1st gear. I guess this teaches one to be gentle with the clutch, to eliminate jerky starts.

I'll have to see if my Mazda 3 will be able to roll in 3 or 4 without stalling. I'm curious. As for the technique you describe, that's how I generally teach people inexperienced with driving stick. I get them to get the car moving in first without using the throttle to get a sense of where the grabbing/release point is, and it also nips bad habits like throttling hard and aggressively slipping the clutch before they can start to form.

Machine Elf
07-23-2012, 08:06 AM
Do you mean if I were to drag race an automatic car, all I have to do is floor the accelerator?

Got an auto-trans car? Next time you're all alone at a red light, floor the accelerator when the light turns green: you'll see the tach touch redline just as the transmission shifts into second (and third, and overdrive, if you care to get going that fast). Can't do much better than that.

People who turn street cars into competition drag racers will refit their cars with (among other things) a couple of helpful features:

-a torque converter on the transmission with a stall RPM that's maybe 1000-2000 RPM below the RPM at which the engine delivers peak torque, and

-a rev limiter that interrupts the spark at an RPM just below the torque converter's stall RPM, until the driver releases a switch (at which point the original redline RPM limiter is restored to duty).

So when you're a couple of seconds from launching down the track, you hold the button for the low-RPM rev limiter, and you flatfoot the throttle. The low-RPM rev limiter holds the engine at maybe 3500 RPM or so, just below the point where the torque converter starts delivering heavy torque. When the tree turns green, you release the switch, the engine starts delivering all its power, and now the rev limiter lets the engine spin up - and it only has to spin up a little bit before you start getting full torque delivery. Yahoooooooo....

WilliamII
02-04-2016, 07:25 PM
The main reason to downshift gears with an automatic transmission is when going
down steep hills to get engine braking and thus save your brakes. I have D, 3, 2, and 1 on my car (2007 Buick Lucerne). I downshift to 3 (direct drive) when going
down a long steep hill (like the Merritt Pkwy in Connecticut) and doing over 65 mph. This keeps me from having to use the brake as much plus gives me better control of the car going around sharper curves. I will use 2 only if I am under 65 mph and going down an extremely steep hill. I do believe that my car, if I came to a complete stop with the shifter in 2, would shift all the way down to first gear. I never use 1 gear (can only shift into it if I am going slower than 25 mph), but would consider using it if I was on snow/ice and going down an extremely steep hill at low speed.

People who keep their automatic transmission in D all the time simply don't know
how to drive. Truck drivers downshift their big rigs going down steep hills all the time to avoid undue strain on or completely losing their brakes. A driver with an automatic must do basically the same thing, except without a clutch and manual gears that a truck has.

I. Dunno
02-05-2016, 03:22 AM
Do Zombies prefer automatics or sticks?

And while I'm here, Fords and Mercs (Crown Vics and Grand Marq's) that I've had would lock into 2nd if that was selected. So the vehicle would both start and stay in 2nd. Seems like my long gone 71 AMC Javelin did the same. So not all vehicles shift 1-2 if put into 2nd.

bob++
02-05-2016, 05:34 AM
Interesting thread and demonstrates how fast technology is moving on. I drive an auto Ford in the UK and, like most modern atomatics (stick still rules here), it has a six speed "powershift" gearbox with twin clutches.

Most of the comments above refer to fluid transmissions. My car, like most today, does not have fluid, but the gear selection is done by a computer. I don't have 1,2,D,N,R,P but D,N,R,P. I do, however, have a manual override, so I can force a downchange on a long downhill section. I also have a (rarely used) "Sport" mode, which delays upshifts to a higher RPM.

The trucks (44 tonne semis) that I used to drive had very similar gearboxes, only with 12 ratios instead of 6. For downhill stretches I also had an exhaust brake which was made more effective when the revs were raised by forcing a downshift - In these circumstances, the computer recognises what's happening and doesn't try to upshift until the throttle is applied again. After driving complex manual trucks, switching to auto required a complete re-think.

Boyo Jim
02-05-2016, 08:57 AM
Sorry for a brief hijack -- what is the right term for an automatic transmission that lets you manually select from all the forward gears (mine has six) rather then letting the system choose its own shift point? The manual says "manual transmission" which doesn't seem right to me because there's no manual clutch.

Telemark
02-05-2016, 09:04 AM
Manumatic (https://en.wikipedia.org/wiki/Manumatic), or many proprietary names.

HoneyBadgerDC
02-05-2016, 09:31 AM
I live in Ca. we have a lot of mountains here with steep winding roads and long grades. I am always shocked at how many older drivers have never learned to use the gears. I seldom ever touch my brakes in the mountains, in most cases second gear works perfectly with no need for breaking. The only problem I have had a few ties is forgetting to take the car back out of second when I hit level ground and traveling too fast in second causing the transmission overheat light to come on. When this does happen I shift into high and slow down to about 65 mph. It takes about 10 min for the light to go back off.

bardos
12-17-2016, 01:07 AM
Zombie thread revival: I just bought a used car with an automatic transmission with D, 3,2 and L. So it's a 4 speed automatic. Now I understand, and use the advice of, all the previous comments about downhill driving and icy conditions, etc. However I have another contribution and possibly a question to pose at the same time.

When mpg specs are given for a specific model of car, you may see, as an example, the following: 24mpg city, 29mpg highway with automatic transmission. The next line will have the mpg for manual transmissions which will always be a few mpg higher.

I don't know exactly why the above fact seems to always be the case, but... if I drive my 4-speed automatic as if it were a stick shift, will my mpg increase?

bob++
12-17-2016, 06:05 AM
Older automatics with a 'fluid flywheel' (https://en.wikipedia.org/wiki/Fluid_coupling) waste power churning the fluid around. There is also a small weight penalty. A good driver with a stick will always beat an automatic, because they can anticipate what is ahead. The automatic can only react after the event.

Of course a propery set auto will always beat a badly driven stick, but autos are getting more sophisticated and will soon be hard to beat anywhere.

leftfield6
12-17-2016, 07:01 AM
Zombie thread revival: I just bought a used car with an automatic transmission with D, 3,2 and L. So it's a 4 speed automatic. Now I understand, and use the advice of, all the previous comments about downhill driving and icy conditions, etc. However I have another contribution and possibly a question to pose at the same time.

When mpg specs are given for a specific model of car, you may see, as an example, the following: 24mpg city, 29mpg highway with automatic transmission. The next line will have the mpg for manual transmissions which will always be a few mpg higher.

I don't know exactly why the above fact seems to always be the case, but... if I drive my 4-speed automatic as if it were a stick shift, will my mpg increase?

Almost certainly not. A well designed, properly functioning automatic transmission will shift more efficiently if left to it's programming. As a matter of fact, even your statement about manuals always having a better mpg rating is no longer true. As mentioned in this article, automatics have improved to the point where they get the same, or in some cases, better mpg.

Here is another SD thread on this same topic. (http://boards.academicpursuits.us/sdmb/showthread.php?t=599174)

jz78817
12-17-2016, 08:25 AM
Zombie thread revival: I just bought a used car with an automatic transmission with D, 3,2 and L. So it's a 4 speed automatic. Now I understand, and use the advice of, all the previous comments about downhill driving and icy conditions, etc. However I have another contribution and possibly a question to pose at the same time.

When mpg specs are given for a specific model of car, you may see, as an example, the following: 24mpg city, 29mpg highway with automatic transmission. The next line will have the mpg for manual transmissions which will always be a few mpg higher.

I don't know exactly why the above fact seems to always be the case, but... if I drive my 4-speed automatic as if it were a stick shift, will my mpg increase?

It's not "always" the case, and hasn't been for a while. it's historically been the case since years ago the choice was between a 3-speed automatic without overdrive or a lock-up torque converter and a 4- or 5- speed manual with overdrive. the difference in fuel economy was significant.

once automatics reached forward-gear parity with manuals, the fuel economy advantage of manuals was minimal. And once automatics surpassed manuals in the number of forward gear ratios, manual transmissions had no advantage. Manuals are pretty much topped out at 7 speeds. GM and Ford have just launched a 10-speed auto.

HoneyBadgerDC
12-17-2016, 02:38 PM
I use my gears constantly in mountain or downgrades. I never like to use brakes to control my downhill speed. I shift as low as I need to go to avoid using my brakes. I have on occassion forgot to upshift when I was back to highway speeds causing the high temp light to come on for my transmission. Important to put back in drive when back to highway speeds.

watchwolf49
12-17-2016, 03:53 PM
I have an automatic right now for the first time in a God awful long time ... so far I've never had the occasion to downshift when going downhill ... but then I don't accelerate between the hairpin curves ... I figure a few seconds braking every minute or two doesn't really overheat them ... even in overdrive I slow down just idling the engine ...

Uphill I try always to downshift ... run up the engine to about 3500 rpm and I seem to have plenty of power while not lugging the engine ...

... but then again the twisty steep mountain roads around here are far far more beautiful at 15 mph than at 40 mph ... think US-199 in Northern California ...

Dr_Paprika
12-17-2016, 04:47 PM
I miss driving a manual car, hope my next one is.

Backing up, getting towed, going through car washes, very icy road, very steep hill, parking... Most of my time is still in D.

Shagnasty
12-17-2016, 05:36 PM
It's not "always" the case, and hasn't been for a while. it's historically been the case since years ago the choice was between a 3-speed automatic without overdrive or a lock-up torque converter and a 4- or 5- speed manual with overdrive. the difference in fuel economy was significant.

once automatics reached forward-gear parity with manuals, the fuel economy advantage of manuals was minimal. And once automatics surpassed manuals in the number of forward gear ratios, manual transmissions had no advantage. Manuals are pretty much topped out at 7 speeds. GM and Ford have just launched a 10-speed auto.

Right. I know how to drive a manual just fine. I even had one for many years. However, they are not superior in any way to modern automatic transmissions. My father has a Corvette Z-07 (the track ready version of the Z-06) and it is stupid fast. It is offered in both the automatic and manual transmission versions. Guess which one is faster even with professional drivers? It is the automatic because no human can shift through 8 gears as fast as a computer controlled transmission can. It gets better gas mileage than the manual version as well.

It is time for the idea that automatic transmissions are inferior to manual ones to die because it simply isn't true anymore. It also isn't true that manual transmissions offer more control. Most modern automatic transmissions offer a range of settings. Most people don't ever use most of them but they are there. My Toyota Rav4 for example will let you downshift (I have used that on icy downhills), lock in 4 wheel drive (never used it) or turn off traction control (used that when I was stuck in a rut).

If someone doesn't know what all those extra settings are for on their vehicle, I would suggest some self-taught remedial driver's ed. Find a large parking lot or an unpopulated road and try them out at lower speeds. You won't hurt anything as long as you don't try to drop into 1st gear at 70mph. I do something similar at the start of every winter. I find a snowed in parking lot and practice skid and spin recovery. It is a lot of fun and may look to others like I am just goofing off but that isn't the point. I need to know intuitively how my vehicle will react under unusual circumstances and that knowledge has served me well so far.

watchwolf49
12-17-2016, 05:47 PM
The only argument I have with Shagnasty's comments is manual transmissions are cheaper ... unless one is doing A LOT of towing, then the costs of replacement clutches will tip the balance back to automatics ... that's direct from Click and Clack ... the second and third smartest humans ...

jjakucyk
12-17-2016, 10:48 PM
One thing automatics don't do by themselves is downshift when the intention is to slow the vehicle, which would save gas over staying in gear and using the brakes. It doesn't do it because the car has no way of knowing if you're coming to a stop ahead or if you just want to coast. The latter is a safer bet from a fuel economy point of view, and in general an automatic tries to stay in as high a gear as possible for the same reason. Electric cars for the most part don't coast, they slow down hard when you let your foot off the accelerator (I think some Tesla owners can drive without using the brake pedal at all) which is fine because it captures that momentum via regenerative brakes to recharge the batteries, whereas an internal combustion vehicle loses that momentum as heat through engine/gearing friction or brake friction.

Anyway, I almost always downshift using the Tiptronic (manumatic) mode when exiting a highway or coming to a stop on a higher speed road. This keeps the engine RPMs above the overrun cutoff threshold where the electronic fuel injection system stops all fuel flow to the engine (in the case of my car that's around 1,400 RPMs) as long as there's no throttle. On an automatic in "D" coming to a stop, because it tries to stay in as high a gear as possible to maximize the car's coasting ability, it can drop below the overrun RPMs around 50 mph or so. At that point, gas is supplied to the engine again to basically keep it idling. The same is true for a manual with the clutch depressed and using the brakes to slow down.

I don't generally downshift to 1st gear because it's so low that it makes the car lurch, plus by then the car is below 25 mph, so it would only rev the engine for a second or two and not give much benefit. Interestingly, I can't start my car in 2nd gear from a complete stop, just if it's barely crawling along. This is a 5-speed automatic 2002 Passat V6. I've driven some newer Jettas with 6-speed automatics, and those I could start in 2nd. It make sense with closer gear ratios and a lighter weight car.

Rick
12-17-2016, 11:38 PM
) You won't hurt anything as long as you don't try to drop into 1st gear at 70mph.


Hell go ahead and put it into 1st at 80, you won't hurt anything. The computer knows what RPM a particular gear would give at any speed. The computer isn't stupid.
I have paddle shifters on my Hyundai. Coming to a freeway ramp @ 80MPH I start pulling on the down paddle 5-4-3 and at about 40 another pull gets 2nd. At a bit below 30 a pull will get 1st.

Melbourne
12-18-2016, 01:16 AM
Looking it up, it does seem that in a lot of automatics these days, 2 means "second gear only" and not "first and second." I could swear my in my 80s and 90s era automatics, "2" meant limiting the gears to first and second, but perhaps I was not as observant back then as I am now, as I didn't drive sticks until the late 90s.

In my car now, it's a sort of computer control, not the old style hydraulic control. The gear lever only has plus/minus, it doesn't actually tell the car what gear to be in.

In manual mode, it never changes up, but it will change down,

The only time this is really useful to me is at the bottom of a steep dip. I can push it into 5, it doesn't go up a gear into 6 as I coast down, it doesn't have to change back from 6 to 5 as I start up the other side.

From standing, it always starts in first, and in "manual" mode will rev right up to the engine safety limit without changing gears. But starting from drive / six, I can force it down to 5, and provided I never slow down enough to make it drop another gear, it will stay in 5.

Richard Pearse
12-18-2016, 05:57 AM
The only argument I have with Shagnasty's comments is manual transmissions are cheaper ... unless one is doing A LOT of towing, then the costs of replacement clutches will tip the balance back to automatics ... that's direct from Click and Clack ... the second and third smartest humans ...

Replacement clutches? I've never had to replace a clutch on a manual car.

CoastalMaineiac
12-18-2016, 11:09 AM
Manual transmission guy speaking here: I drive a 5-speed 2007 Mustang GT. Nice little entry-level "performance" car.

Typically, you want the lower gears for either speed limiting (going downhill without wearing out your brakes) or for passing. I'll discuss snowy driving as well (I live and drive in the upper midwest, where snow, ice and sleet are common in winter months.)

If you have a long downhill stretch (mountains) it may be better to keep the car in a low gear (probably 2nd) to ease the load on your brakes. This is more applicable for semi trucks - they're huge, heavy, and they can absolutely ruin their brakes and lose control if they don't downshift on long hills. But most cars can handle the braking necessary on long downhill stretches, unless you're doing it every day, repeatedly. But it is helpful. I do have one steep hill in my normal driving area; when I'm going down it it's nice to just put the car in 2nd to have more speed control and not have to stand on the brake pedal.

3rd gear on most cars is a good "passing" gear - meaning, you're on the highway, you want to pass someone. 3rd gear is good for getting reasonably quick acceleration without putting your tach into the redline. I do this all the time. The difference here between manual and auto trannys is that in all the autos I've driven, you shift to the left (passing) lane, floor it, and whatever controls the auto takes a few seconds to realize you really want to go fast. In a manual, you just shift and go.

As for snow/ice - and I say this driving a RWD Mustang near Chicago (So I am familiar with driving in snow with a car totally unsuited for such a thing):

If you get stuck on a slippery area, having control of the gear is very helpful. An earlier poster suggested that 2nd is the gear you want; I disagree, at least for my vehicle. What you really need to do to get moving on snow or ice is first: Disable traction control. Traction control kills power to the wheels if it senses that they're slipping. Traction control is a great safety feature when the car is in motion; it's terrible for getting the car moving.

Personally, I've had the best luck putting it in 1st with traction control off, and giving it a good amount of throttle. Often you end up going forward a bit, then losing traction and spinning the wheels. Then you want to put it in reverse, and again, give it a good amount of throttle. I usually end up rocking back and forth a bit, but I've never gotten stuck. Just keep rocking back and forth until you get the momentum to keep going.

Once you're moving on snow and ice, absolutely turn traction control back on. It really is a good safety feature, it just makes it harder to get started.

I've heard that professional truck drivers are taught to use lower gears when climbing a hill, as opposed to higher gears. It's better to rev higher on the tach and have to ease off the throttle if your wheels start to spin, than it is to have to ease off the throttle AND downshift or risk stalling.

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