How does "Park" work in an auto transmission

[dsmith41]

Back in the day when I was driving a manual, I would always leave the vehicle in gear with the e-brake on. These days I have an auto in my truck but just out of habit, I always set my e-brake when the vehicle is in park.

Recently with the record cold temps we have been seeing, my e-brake likes to freeze up so I have not been using it. This bothers my OCD because I am used to setting the brake and the thought of my transmission holding the entire weight of my truck in park annoys me. I know most people do not set their e-brakes and it makes no difference in transmission longevity but I was wondering how the park gear works. How does it lock the vehicle in place? What kind of mechanism is it?

 

[hate2work]

I wouldn't park on a hill using just my tranny in Park, but on flat ground I would trust it.

Maybe you could buy some cheap wheel chocks to use?

 

[TallPaul]

As I understand it and it may have changed since then, but park is a pin or more accurately a pawl, that drops into a hole or notch and holds it from moving. That explains why if you put it in park on a steep hill wihthout the parking brake it can be hard to pull out of park and goes out with a bump as the pawl releases suddenly.

With an automatic I always use the parking brake on a slope, but in my garage, never. Use it or lose it. It will freeze up if left unused for years.

 

[Gradient]

HowStuffWorks

 

[dsmith41]

Originally Posted By: Gradient
HowStuffWorks


That little tapered pin doesn't look too stout.

 

[wirelessF]

It also puts stress on the drive components as well (u-joints, cv-joints, etc.)

 

[TallPaul]

Just more reasons to drive a manual.

 

[Blokey]

...or set your e-brake before putting the car in park.

 

[mechtech2]

Concerning parking brakes:
Use them all the time or never. And I have learned not to use them in temperatures of 15 deg F or below.
Even many mfrs. warn about this [because of freezing].

Parking pawls inside auto trannys seem under -engineered. But they are not failing, somehow. It is very very rare to see on go out in normal use. If someone jams it it park while moving, it can happen [very rare]. The one time I know of for sure that a pawl system broke is when a vehicle was struck when it was parked.
It broke the trans internally at that point, and needed a new trans for that stupid little extension.

 

[wirelessF]

Originally Posted By: TallPaul
Just more reasons to drive a manual.


You can do the same with an MT. Put it in gear and it will rock back as you let go the brake pedal, same as an AT.

 

[dsmith41]

I was expecting this thread would convince me there is no need to use the e-brake when in park but that's not the case. I'm gonna keep on using it. And I thought I was weird for using all the time.

 

[TallPaul]

Here is a great story. When I was a teen, I once threw my '71 Ford with a 302 V8 (that's a 5.0 for you young whippersnapers) with a C3 automatic into park doing 30 mph. It sounded like an extremely loud ratchet as I rolled into the burger joint and all the customers were staring at me out the window. Once it got slowed down enough it lurched to a stop as the pawl dropped into the slot. Park still worked after that.

 

[TallPaul]

Originally Posted By: wirelessF
Originally Posted By: TallPaul
Just more reasons to drive a manual.


You can do the same with an MT. Put it in gear and it will rock back as you let go the brake pedal, same as an AT.
True, but consider if you let gravity rest on the park pawl vs gravity resting on the clutch. Then hold the break pedal down and pull it out of park, it will be tough, whereas the clutch will disengage normally.

 

[ClarkB]

Since this argument has come down to how much work is required by the driver, I find it difficult to think that using your left foot to work the clutch is less work than taking a vehicle out of park when it is on a hill. Or would that actually be a reason to own an automatic?

Clark

 

[BearZDefect]

Originally Posted By: wirelessF
It also puts stress on the drive components as well (u-joints, cv-joints, etc.)
And engine mounts.

I use the parking brake out of habit, and when parked on a hill I make sure the stress is on the parking brake instead of the pawl.

But as others wrote, on almost level ground, the park pawl is more than adequate.

And, as already stated, you put the same stress on the joints and mounts with a manual transmission if you let the engine hold the vehicle on a slope in gear instead of the parking brake. With a MT I always park in low gear, but consider that a backup in case the parking brake fails.

 

[bigmike]

Originally Posted By: dsmith41
I was expecting this thread would convince me there is no need to use the e-brake when in park but that's not the case. I'm gonna keep on using it. And I thought I was weird for using all the time.


I grew up driving a manual, so I'm like you. I use my e-brake in my automatic religiously. I even managed to convince my wife to do so.

 

[Gary Allan]

I can't trust the engine compression to hold my wife's jeep. I rolled into the dealer and parked it to get parts. While I was 'hitting up the parts MAN, a polished sales type came in and asked "who owns the white Wrangler?". He took me out and, on just a slight incline, my wife's jeep slowly chugged across the parking lot and hit a new car. The damage was minimal.

I think it's the cam overlap that they need to have the 4.0 handle NOX without an EGR.

 

[TallPaul]

My 77 F150 parking brake froze and as a teen I didn't fix it, so every morning my truck was at the bottom of the driveway. Eventually I got into the habit of sticking a piece of wood behind the tire when I parked.