Dear Tom and Ray:
On a recent visit to my home, my "wonderful" mother expanded her range of "helpful" advice-giving to the manner in which I park my car on my steeply sloped driveway. She was deeply concerned about the order in which I engage park and the emergency brake. She advised me that by placing the car in park first and then engaging the emergency brake, I am sure to ruin the transmission. Her motherly recommendation is, of course, to reverse the order, thereby saving the world. I've been unable to find either a confirmation or a denial regarding the proper order for my parking procedures. Would the brothers be willing to provide a final word on this matter? Thanks. — Lynnay
Tom: Lynnay, we're going to use the worst four words an adult daughter can hear: Your mother is right.
Ray: Well, her instructions are right. She's wrong about the severity of the consequences, but she is correct that the preferred parking method on a hill is to deploy the parking brake first, to hold the car in place, and then put the transmission in park, to back up the parking brake.
Tom: Here's why. Park works by using a ratcheting mechanism called the parking pawl to lock the output shaft of the transmission. Because of the way the differential works, locking the output shaft allows the driven wheels to turn only if they move in opposite directions. So unless the car is being dragged or it slides (which ain't easy if you're a car), once it's in park, it's not going anywhere.
Ray: But because of the way that ratchet system is designed, if you put the car in park and then it rolls up or down a hill a few feet, the weight of the car ends up resting on the parking pawl, pushing it in tighter than it needs to go.
Tom: Will that ruin your transmission? No. But it can make it hard for you to get the car out of park when you go to drive away. Maybe you've even noticed this.
Ray: This is especially true of older cars, where these parts have started to wear out and create "slop," or in cars that have been parked incorrectly on hills for many years -- like yours! Of course, it matters only on steeper hills.
Tom: By applying the parking brake first, you allow the brakes to do the job of holding the wheels in place, so the car doesn't roll and push the park mechanism to the point where it's difficult to remove.
Ray: Then, when you drive away, you do the opposite: You take the car out of park first, and then release the parking brake.
Tom: I know this is a tough blow to absorb, Lynnay. But just remember, this could be a completely isolated case of Mom being right, and have no bearing on whether she also was right about your first three husbands.
(Car Talk is a nationally syndicated column by automotive experts (and brothers) Tom and Ray Magliozzi. Write to them at the Car Talk website.)
4 Comments
By mkt on September 14, 2012 10:43 PM
Why does engaging the parking brake make a difference? I've got my foot on the regular brake the whole time during these procedures -- isn't that just as good as this advice to engage the parking brake first?
By Hoof on September 15, 2012 2:21 PM
On most cars, the parking brake actuates a different mechanism than the hydraulic foot brake. There is some "slop" in this mechanical mechanism which is taken up when the car rolls backward a tiny bit after you release the regular brake pedal. (on a steep hill)
The answer to your question is found by observing whether or not the car moves (at all) after you remove your foot (from the regular brake) when you park your way on a steep hill. If it doesn't, you're fine. If it does, you should do it "their way", which is, precisely: 1. foot on regular brake. 2. transmission in neutral 3. actuate parking brake 4. remove foot from regular brake. 5. transmission in park.
By Ross on September 18, 2012 3:04 PM
I disagree with the answer given. I have been a participant in cleaning up the mess after the brakes have failed and the park position failed to keep the car from moving. It was found that the sudden slam created by the brakes failing over whelmed the pawl position which broke. It is true that steep hills can add pressure to the parking pawl but park needs to be engaged first so that some of the weight of the car can be applied against the pawl before the brakes thus removing the "slop". In our society there is often a curb and correctly placing the wheel against the curb will go a long ways towards preserving both the park pawl and the brakes.
For those who think the brake mechanisms are different between emergency and foot brakes, you are correct only in the zone between application and effect. The brake itself is operated by two separate systems. That is one reason why catastrophic failure of the emergency brake is sometimes followed by a broken pawl. Furthermore, the placing of the transmission in park is often prevented if the foot brake is not applied first. This prevents damage to the transmission.
To recap:
First stop car and turn steering to place wheel against the curb; let the car roll a small distance if needed(either forward or back depending on which way on the hill you are parking--the front of the wheel will be against the curb if you are parking downhill but if parking uphill the back of the wheel will be against the curb).
Second place car in park and ease the car against the pawl without removing foot from brake.
Third apply emergency brake so that the second system keeps the brakes fully applied.
The result is a car that is secured with a wheel chock(the curb), and a transmission in the park position, and a fully applied emergency or parking brake.
By Stevie Rave On on September 23, 2012 4:39 AM
What about with a manual transmission?