Parking Brake on Auto Transmission Cars

Friendly debate here at work:

I’ve NEVER used my parking brake on any of my auto-transmission cars, BUT a co-worker of mine ALWAYS uses her’s. She says it takes the “pressure” off the transmision even when it is in park.

It certainly can, and how the sequench of application is important. The only other thing holding the car if no parking brake is used is the parking pawl in the tranny which keeps the gears from allowing the car to roll. Always good to keep the parking brake in good working order anyway, or if not use can cause other problems with corrosion, locking, failure to work, etc.

She’s correct. The transmission is designed to DRIVE the car. The parking brake is designed to hold it in place.

The parking pawl in the transmission, which is what keeps the car from moving when it’s in park, is a small piece of metal, maybe 1/2 inch in diameter. You are asking it to hold the entire weight of your car, which is 1.5 to 2 tons. That’s a lot.

I always set the parking brake on my cars, one of which has an automatic transmission.

She is correct. Proper procedure is the engage the parking brake before putting the transmission in Park. This reduces or eliminates pressure on the parking pawl in the transmission. If you only park in places that are absolutely level, this won’t really matter. However, there are a couple of other factors to consider:

  1. You may need to have a functioning parking brake to pass safety inspection. If you never use it, the cables are likely to rust solid, and you’re facing a repair bill.
  2. In some vehicles, the rear drum brakes are only adjusted by using the parking brake (e.g. later model Chrysler minivans). If you don’t use the parking brake, the rear brakes get out of adjustment, which can throw off brake balance and/or increase stopping distances.

Reasons to always use the parking brake.

  1. It reduces the strain on the transmission if you are parked on an incline. Sometimes automatics can get stuck in park if you don’t.
  2. It’s redundant braking, so now two things must fail before the car moves.
  3. It keeps the parking brake working, just in case you need it in an emergency.
  4. When you just put the transmission in park, if one drive wheel does not have traction, the other one will move freely due to the action of the differential.

You can count this as one more vote that supports your co-worker’s practice of using the parking brake. The preceding posts have summarized the reasons very well, so hopefully you will heed this information and begin to use the parking brake.

2007 in Bangor Me. people sent two cars into the river when their cars weren’t parked with the parking brake. Maybe they forgot to put it in park or in gear but it would have been worth it to them to use the parking brake. Many problems are caused by cars that slip out of park when they are on steep hills.

The park brake adjusts the rear brakes if the vehicle has rear disc brakes. Also if you have transmission damage, insurance companies will not cover any damage if the park pawl is sheared from not using the park brake.

In short, use the parking brake as the primary method of keeping the car where you parked it. Use the transmission as a way of delivering power to the wheels and as a backup to the parking brake.

My 2 cents; I agree with ALL the posts above.

Once, when my wife failed to set the parking brake on a borrowed car, we were very fortunate in two respects. First, the borrowed car was an older Volvo, so it was built like a tank and sustained no damage when it rolled across a parking lot and hit another car - we didn’t lose any friends on that one. Second, the car that it rolled into and left a giant dent in was our own car - so there was no need to deal with an angry person (except me) or anyone’s insurance company. We just live with the giant dent.

That’s about all I have to say about it.

It adjusts read drum brakes. Disks don’t need adjustment.

But with the right leverage, a three year old could hold a 1.5 to 2 ton car. The parking pawl sees considerable stress, but let’s not go making it sound as if they are prone to failure.

I wonder why driving instructors don’t teach new drivers to set the parking brake before leaving the vehicle. I almost lose a few fingers when someone was jacking a rental car as I swapped tires, obviously parking brake was not set. BOOM! The car roll off the jack.

Do a search on this forum. People that are in the habit of not using the parking brake have been complaining about difficulties getting the car out of ‘Park’. A lot of it due to bent parking prawls that increasing become difficult to engage and dis-engage. Not using the parking brake can lead to expensive consequences.

That’s not always true. Look it up. My car has the parking brake as part of the rear disc. The rear calibers have a screw-in type piston. It self adjusts to keep the pads close to the disc so that the parking brake feature will work.

Are you ready to beg for mercy from your coworker yet? She is right and you are wrong.

WOW, thanks for all the info! When I parked today I used the parking brake. I’ve lost this “bet”.

This is not entirely true.
On several cars the park brake is incorporated into the rear calipers. When the park brake is activated the piston is ratcheted out a bit to keep it adjusted to the rotor. On others there are small shoes that press out into a drum portion of the rotor. Like an old Corvette or an old Volvo 240 or 260 series.

Point taken. But as written it looks like you are saying that it is only important to use the parking brake to adjust the rear brakes if they are disks, which is not so. Many rear drums are adjusted by applying the parking brake.

Edit: spelling