Parking pawl damage when raising car with auto trans?

[Kurtatron]

I’ve always owned Manual transmissions. Now that I own automatics, I am confused about jacking them up.

When I put a car in park, the car rolls forward or back depending on the road’s slope. Then something catches and stops the rolling.

In my mind, I wonder if you jack a car up, say the rear on a fwd car, aren’t you rotating the wheels against the transmission engaged in park?

It’s clear to visualize a manual transmission in 5th gear. Jacking it up will rotate the engine. So in an automatic, is there risk of damaging the parking pawl or something if you jack it too high?

Also, I was working on my Ford Focus yesterday. Even though it was in Park, the wheels spun freely while airborne. Why??? If the car is in park, why doesn’t it roll freely if the wheels roll freely when jacked up?

Automatics confuse me I tell ya.

 

[spasm3]

With the drive end jacked up, if you spin one wheel, the other probably spins in the opposite direction.

 

[TheOilWizard]

I’ve always owned Manual transmissions. Now that I own automatics, I am confused about jacking them up.

When I put a car in park, the car rolls forward or back depending on the road’s slope. Then something catches and stops the rolling.

In my mind, I wonder if you jack a car up, say the rear on a fwd car, aren’t you rotating the wheels against the transmission engaged in park?

It’s clear to visualize a manual transmission in 5th gear. Jacking it up will rotate the engine. So in an automatic, is there risk of damaging the parking pawl or something if you jack it too high?

Also, I was working on my Ford Focus yesterday. Even though it was in Park, the wheels spun freely while airborne. Why??? If the car is in park, why doesn’t it roll freely if the wheels roll freely when jacked up?

Automatics confuse me I tell ya.

Interesting, I wouldn't expect that either. It appears that what @D60 is correct, that the Focus transmission is operating like an open differential, so the tires spin in opposite directions.

 

[D60]

You won't hurt the pawl unless maybe you're winching against it. Even then tow trucks pull 'em out of spots all the time and just skid the tires. It ain't great, but usually not a problem.

Think of your situation like this: the park pawl is there specifically to hold the weight of the vehicle even when parked on a hill in San Francisco or the Virgin Islands (holy crap they pave some steep stuff!!). So you're not doing anything more than that.

Finally, with a peg-leg (open diff) any TWO of the three will spin: the three are axle, axle and d/s (or trans output).

In park your trans output is locked but both wheels were free to spin. If you block one wheel, the other should not spin because the other TWO of THREE are now locked. Conversely, you could block the other wheel but put the trans in N and then spin a wheel.

Clear as mud? Speaking of mud, see also: My Cousin Vinny regarding open diffs

 

[D60]

^note this is also why fakey brake "lockers" work. If you BRAKE the wheel in the air that wants to just spin wildly (My Cousin Vinny, in the GA mud), it FORCES the other wheel to turn, effectively making an open diff a locked diff.

However TC systems use computers to CONSTANTLY check the wheel speed of the tire in the air or in the mud and chatter like crazy because they release that wheel, see wheel speed is too high, lock ONLY that caliper, and repeat. Several times per second. Release, check, lock. Release, check, lock.

 

[Dave Sherman]

I've not heard of damaging a parking pawl that way. The pawl can take the weight of the car sitting on a hill, though in the days of cable operated linkages I'd have to pull harder to pull it out of park if it had the weight against it. I always use the parking brake on a hill to avoid that. Even if the wheels on the ground were immobilized by a chock or parking brake, jacking it up I would think the tire has enough give to get the wheel being jacked up off the ground.

 

[IndyIan]

Interesting, I wouldn't expect that either. It appears that what @D60 is correct, that the Focus transmission is operating like an open differential, so the tires spin in opposite directions.

If both are in the air, they will counter rotate even in Park.
I had a lesson on why brakes are put on all 4 wheels with my 4wd tractor, when I was driving down a muddy hilly, and let off the HST pedal which brakes the diffs, and watched in amazement as the tires start counter rotating, the 2 on the left turning backwards! and the tractor slowing slightly but not stopping! Then I hit the brakes which is only on the rear axle which stopped them from counter rotating, and slowed me down a bit more, but the fronts were still counter rotating. Fortunately the mud ended and as I got onto grass the front tires dug in. Ag tractor tires are also directional, set up to clear out the tread when pulling, not stopping, which made things worse.

The lesson is to put on the rear parking brake when jacking up one side of a car, or it could roll forward or back.

 

[LostInTransit]

Here's a for instance, if you have a front wheel drive vehicle and jack up the rear of the car, it would move forward slightly because of the small amount of play in the CV joints. One would need a block to place under the front tire. The bad side of this is if it did move forward, it would be hard to remove the block from the front tire.

 

[RedSpider]

You're not going to damage the parking pawl on the automatic just by jacking it, but regardless of whether its a stick or auto, FWD or RWD or AWD/4WD, if you're jacking the car the parking brake should be on and at least one other wheel should be chocked making it a moot point.

 

[lbhsbz]

The floor jack has wheels....no? Every time I've jacked up a non-driven axle or any axle with the other end of the car chocked, the jack rolls to where it needs to without dragging the car. Squirt some lube on the jack wheel axles every 10 years or so and it helps it along some lol.

 

[Kurtatron]

Here's a for instance, if you have a front wheel drive vehicle and jack up the rear of the car, it would move forward slightly because of the small amount of play in the CV joints. One would need a block to place under the front tire. The bad side of this is if it did move forward, it would be hard to remove the block from the front tire.

I’ll have to watch this next time I jack up the car. A very interesting explanation.

 

[nascarnation]

At GM in my era there was a spec for park pawl durability.
You took a vehicle at max spec GVW and applied the pawl above the rachet speed and coasted down until it latched in.
Can't remember how many times it had to survive this but it was double digits.
So no worry about your jacking situation.

There was also a bump test where the vehicle was stationary in park and a weighted sled running at low speed (can't remember the speed, maybe 2.5 mph) impacts it front and rear and it had to stay locked.

 

[Donald]

At GM in my era there was a spec for park pawl durability.
You took a vehicle at max spec GVW and applied the pawl above the rachet speed and coasted down until it latched in.
Can't remember how many times it had to survive this but it was double digits.
So no worry about your jacking situation.

There was also a bump test where the vehicle was stationary in park and a weighted sled running at low speed (can't remember the speed, maybe 2.5 mph) impacts it front and rear and it had to stay locked.

Decades ago there were some cars that got recalled as the cars jumped out of park and ran over the driver as the driver got out to get the mail.

 

[Bailey28]

We put Crown Vic's into park at 10 mph while jumping out upon occasion..never broke those pawls in their trannys...

 

[LostInTransit]

I’ll have to watch this next time I jack up the car. A very interesting explanation.

Maybe I'm clueless on the amount of the roll up or back during this isnace as I'm not sure what amount of "play" the CV joints are suppose to have. If these CV joints aren't suspo to have any then I need to have our Van checked out. ideally, I'd like to have a jack stand in place holding the front off the ground or jack stands all around. it could potentially turn into a bad situation if the car isn't more secure when using the roller floor jacks.. I mean the front will move approx 2-4 inches when jacking up the rear of the car. I suspect a bottle jack would be more secure on a flat surface.. but we don't always have flat surfaced to work with.

 

[Donald]

We put Crown Vic's into park at 10 mph while jumping out upon occasion..never broke those pawls in their trannys...

Why would you do that?

 

[Bailey28]

Why would you do that?

To catch a suspect usually running away from you lol.

 

[kballowe]

We drove cars off the assembly line back in the 90's. One of the tests we had to perform was to get the car going and then jam it in park. It was some manner of MVSS requirement to prove that the park pin would not shear. We never broke one.

 

[repairman54]

Decades ago there were some cars that got recalled as the cars jumped out of park and ran over the driver as the driver got out to get the mail.

My old memory says it was some Fords that jumped out of park. Column shifts.