When would I manually shift gears with my automatic transmission?

[watchwolf49]

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]

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]

@Shagnasty

) 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]

@pulykamell

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]

@watchwolf49

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]

@GameHat

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.