Am I going to kill my car by keeping it stopped?
June 16, 2012 11:02 PM   Subscribe

Is it a bad idea to slightly accelerate on a steep uphill slope to keep a car with an automatic transmission stopped?

For no good reason beyond my own amusement, I've taken to keeping my automatic transmission equipped car stopped on a steep uphill slope by very slightly depressing the accelerator pedal. The increased idle speed of the engine keeps the car from rolling backwards. When I need to go forward, I can just depress the accelerator further rather than switching rapidly from the brake pedal to the accelerator pedal. With the slopes in the Seattle area, this is the difference between rolling backwards a foot or so (if I have to switch pedals) and avoiding rolling backwards at all (if I stay on the accelerator pedal).

It occurs to me that I have absolutely no idea if this is a stupid idea, since I haven't found the practice mentioned anywhere, nor has anyone told me to do it or not to do it.

Any thoughts?
posted by saeculorum to Travel & Transportation (23 answers total) 6 users marked this as a favorite
My only thought is: I live in Seattle too and do the same thing. As does my husband and many other people I know who regularly deal with hills on Capitol Hill, downtown or Queen Anne. I have no idea if it's objectively "bad" for the car but I figure it is better than running into the person behind me.
posted by joan_holloway at 11:05 PM on June 16, 2012

If you're worried about stressing your transmission, you could use your parking brake at hilly Seattle intersections. When you switch from brake to accelerator, release the parking brake. That's what I did with my old Saab.

We recently traded it in for an Outback, which is automatic. It has an auto-parking-brake-on-a-hill function which is pretty neat. I don't know if this is a recent innovation or if it's been around for years. When you come to a hill stop, it automatically engages the parking brake, releasing it when you pull away. Depending on how old or new your car is, it might have something like that, perhaps.
posted by Blazecock Pileon at 11:10 PM on June 16, 2012

I learned to drive in Seattle and I was taught that this is why the brake pedal is so big-- so you can have your right foot on it, and put your left foot next to it so you free up your right foot to start depressing the gas while your left foot comes off the brake.

That said, at least with the automatics I've driven, they don't really roll backwards even on steep hills so I've never found it necessary to actually use that method-- I just switch my right foot quickly from brake to gas and I'm fine. Even going up Queen Anne Ave.
posted by rabbitrabbit at 11:13 PM on June 16, 2012 [1 favorite]

Best answer: You are wasting gas, and a moment's inattention could move you either forward or back into another vehicle or pedestrian.
A foot on the brake (or the parking brake) is more secure.
posted by weapons-grade pandemonium at 11:15 PM on June 16, 2012 [18 favorites]

My understanding is that it's not so great for your transmission. Increasing the engine RPM puts more energy into the transmission, which causes it to heat up. Exactly how much I'm not sure; my gut sense is that it's not as bad as, say, towing a heavy trailer, but it is decreasing the life of your transmission and fluid by a non-zero amount vs. using the brakes.

I drive an automatic pickup in Seattle, and what I do on steep hills is use my left foot on the brake pedal and when I'm about to accelerate give it just a bit of gas while easing off the brake to make sure I don't roll back. It takes a bit of practice to get right, but it works well when you do.
posted by hackwolf at 11:15 PM on June 16, 2012 [1 favorite]

Best answer: Your automatic transmission is "slipping", that is, not engaging or disengaging fully.

This means that the components of your clutch pack, in your automatic transmission, are neither spinning freely past each other, nor locked together and transmitting power to the wheels. They are rubbing against each other, modulated by your sensitive foot on the accelerator.

This is wearing the plates in the clutch pack, and heating the transmission fluid. After the clutch plates have worn enough, they won't engage fully, and your transmission will start to slip even when you imagine that it should be fully engaged. Transmission fluid that is heated more often doesn't work as well as transmission fluid that has been well treated.

It's bad. It'll shorten the life of your transmission. Check your transmission fluid: is it dark? Then get it changed. Use your brake. Starting on a hill is easy in an automatic transmission. It'll be a lot less irritating to the driver behind you, too, who probably has some unfavorable opinions of your balancing act, with tonnage, uphill of them.
posted by the Real Dan at 11:34 PM on June 16, 2012 [17 favorites]

Blazecock Pileon, my '92 Subie 5-speed has Hill Holder. It's great! You press the brake like you normally would on an uphill, and then press it a bit further until you feel the tension change, let go, and whammo: no slidey.

OP, use your left foot to brake on the uphills, then roll left-off / right-on when the light turns green.
posted by Chutzler at 11:46 PM on June 16, 2012

You are burning your transmission up, with the bonus of possibly experiencing some interesting new smells.
posted by rhizome at 12:09 AM on June 17, 2012 [2 favorites]

One reason not to do this is that your brake lights won't turn on if you're not stepping on the brake. This could make it a bit easier for an inattentive driver to rear-end you if they don't realize you're stopped. Of course, it takes some real effort to rear-end someone when you're driving up a steep hill, but still.
posted by zachlipton at 12:14 AM on June 17, 2012 [9 favorites]

Best answer: Also, if someone hits you from behind it is very likely you will either jam on the gas from instinct or, even if you don't, be propelled forward into an intersection with no brake drag at the moment of impact.

Don't do that.
posted by spitbull at 12:47 AM on June 17, 2012 [5 favorites]

the Real Dan, I've only owned stick-shifts, but my impression is that automatics generally use some kind of fluid-dynamic torque converter, which can handle some slip for long periods without the kind of rapid wear you'd expect from riding a friction-type clutch. (The wikipedia article on torque converters even says that modern(?) torque converters are designed to be able to be operated in this state for long periods with "little danger of overheating".)

I think 'pandemonium's and spitbull's arguments are better reasons not to do this except briefly; it's too easy accidentally make the car move when you don't intend to.
posted by hattifattener at 1:05 AM on June 17, 2012

Agree. Bad. Others gave better reasonibg as to why, but I specifically remember reading an owner's manual stating NOT to do this very thing.
posted by smalls at 5:06 AM on June 17, 2012

automatics generally use some kind of fluid-dynamic torque converter,
True for the main engine->transmission coupling, but there may be other clutches and brakes inside the transmission, depending on the design.

the owner's manual of my Civic says specifically not to do this:
If you must stop when facing uphill, use the foot brake or parking brake. Do not try to hold the vehicle in place by pressing on the accelerator, as this can cause the automatic transmission to overheat.
posted by ArgentCorvid at 5:56 AM on June 17, 2012 [1 favorite]

(The wikipedia article on torque converters even says that modern(?) torque converters are designed to be able to be operated in this state for long periods with "little danger of overheating".)

This is because the oil cooler for the transmission requires the car to be in motion to work; air must move past it. When you are stopped, this is not the case.

Plus, although the main drive connection is a fluid torque converter, the transmission itself has a series of clutches and valves and so on to drive the gears.

Using the automatic transmission to hold the car is a bad idea.

You won't roll back into the car behind you. Honestly, most people have no idea how small their car actually is.
posted by Pogo_Fuzzybutt at 6:22 AM on June 17, 2012

Best answer: automatics generally use some kind of fluid-dynamic torque converter, which can handle some slip for long periods without the kind of rapid wear you'd expect from riding a friction-type clutch

This is true, and it is indeed the torque converter that's preventing backward slippage in this scenario, so you're not wearing out any rubbing parts.

What you are doing, though, is dumping all the mechanical power your engine is producing into the torque converter fluid as heat. That's not good for the torque converter, which is only designed to dissipate the amount of power produced by the engine at idle; push more than that into it for any length of time and it will overheat.

Best practice for well controlled hill starts is to use the handbrake to hold the car steady on the hill. When you want to take off, press the accelerator slightly before releasing the handbrake. The pulse of heat that this technique delivers to the torque converter is brief enough not to matter at all, and you should find that your takeoff is as smooth as what you've been achieving by riding it.
posted by flabdablet at 7:16 AM on June 17, 2012 [1 favorite]

What flabdablet said. The clutches in an automatic only operate/wear when it is changing gears. When it is in a gear, they are static. Holding on a hill isn't the worst thing in the world for it, but it isn't something you should make a practice of. (Point of fact- my car actually has a hill start assist mode that increases the idle to keep the car slightly rolling forward. If it slips backwards, it will engage the brakes too.)

The only exception to this is if you have a dual-clutch "automatic". They ARE slipping a clutch when you are creeping forward or holding a hill.
posted by gjc at 7:52 AM on June 17, 2012

Response by poster: Thanks for the comments! I have been suitably chastised. I've always known that the handbrake/gas combination (or brake/gas) combination is the best way to start on a hill, but have never properly learned how to. I think this will give me the motivation to start experimenting with the proper technique.
posted by saeculorum at 9:12 AM on June 17, 2012

Thanks for asking this question. I do this on 65th at Phinney all the time; I won't do it anymore.
posted by matildaben at 9:30 AM on June 17, 2012

gjc, flabdablet, and hattifattener are correct, thank-you: the clutch plates are not sliding unless you are changing gears, so the clutch plates should be locked and all spinning together, and the torque converter is doing the slipping and heating. Check the color of your fluid, nonetheless.
Late one night, I conflated transmission failure slippage with torque converter slippage at a stop light...
posted by the Real Dan at 9:43 AM on June 17, 2012

Don't do it, my father and husband will come and yell at you if you do. It is really bad for the transmission, as others have stated.
posted by wandering_not_lost at 6:26 PM on June 17, 2012

Well, it's not reallybad for the transmission because, as some have noted, there is no mechanical wear, although it will heat up the transmission oil and, in theory, deteriorate that oil faster which could lead to faster wear. It's not significant enough to matter in normal driving, though. It's also not very safe, as you run the risk of losing concentration and hitting the car in front of or behind you (human nature being what it is, possible both after you roll backwards into the car behind, then over-compensate in panic so running into the car in front).

Just use your right foot on the brake as normal then, once stopped, put your left foot on the brake to hold it and you can then release the brake at the same time as applying the accelerator. Simple, smooth, safe.

If you have a manual transmission, the situation is very very different - a mechanical clutch means a fried clutch in a very short time if you try and slip it to hold a car on a hill. I've often yelled at my partner and daughter for doing this ;-)
posted by dg at 7:55 PM on June 17, 2012

Just use your right foot on the brake as normal then, once stopped, put your left foot on the brake to hold it and you can then release the brake at the same time as applying the accelerator. Simple, smooth, safe.

Also a horrible habit to acquire if you ever plan to learn to drive with a manual transmission.

Once you've got handbrake-assisted hill starts working well with an auto, it's not a huge stretch to make the same thing happen in a manual - but the manual will need your left foot to operate the clutch. Building muscle memory that says you need it for the brake pedal is therefore most unhelpful.
posted by flabdablet at 8:14 PM on June 17, 2012

I don't really disagree - I was working on the information from others here in previous threads that US drivers are not taught to use the handbrake for hill starts, but to do some weird soft-shoe shuffle involving three pedals and two feet. If you are going to be driving both manual and automatic cars, it makes much more sense to use the same technique for both, sure.
posted by dg at 8:34 PM on June 17, 2012

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