Sloppy Tranny

smkettner wrote:

Sport45 wrote:
We really don't have emergency brakes, we have parking brakes. But p-brake doesn't sound quite right...

The last thing you'd want to do in an emergency is lock up the back tires of the tow vehicle. That's about as close as you can get to a guaranteed jackknife.

Emergency brake and parking brake are the same thing. This brake should be able to lock (skid) the wheel in normal conditions. If not you may need service or adjustment.

If the hydraulic brakes completely fail you might be inclined to risk the jackknife. For best results hold the release lever while you moderate the braking. You may only get one stop so best to completely stop in one motion and wait for a tow. Yes try to avoid skidding to a stop.

I think manufactures took the Emergency out of the Parking brake when they cam up with the press to set, and press to release pedals.

I also remember driving a Chrysler 200 that the Parking brake was a push button! :S

Sport45 wrote:
We really don't have emergency brakes, we have parking brakes. But p-brake doesn't sound quite right...

The last thing you'd want to do in an emergency is lock up the back tires of the tow vehicle. That's about as close as you can get to a guaranteed jackknife.

Emergency brake and parking brake are the same thing. This brake should be able to lock (skid) the wheel in normal conditions. If not you may need service or adjustment.

If the hydraulic brakes completely fail you might be inclined to risk the jackknife. For best results hold the release lever while you moderate the braking. You may only get one stop so best to completely stop in one motion and wait for a tow. Yes try to avoid skidding to a stop.

THanks everybody.
And I have had the trailer jump the first time I camped on a slope. Scared the bejesus out of me, until she settled into the chalks. Now, I always set the chalks, and then put the truck in neutral to let her settle before unhooking. I have not yet mastered the art of leveling, in other words, drive up on the blocks, just a hair past level, so when she settles into the chalks, she's level. Still takes me more than one try.

smkettner wrote:
DID YOU KNOW? Contrary to common thinking, the primary purpose of the transmission's "Park" position (and parking pawl) is to keep the engine's power from reaching the drive wheels when the engine is running, not to stop the vehicle from rolling when parked - this is the job of the e-brake.

http://myautomatictransmission.com/transmission-parking-pawl.htm

We really don't have emergency brakes, we have parking brakes. But p-brake doesn't sound quite right...

The last thing you'd want to do in an emergency is lock up the back tires of the tow vehicle. That's about as close as you can get to a guaranteed jackknife.

ROBERTSUNRUS wrote:
a simple basic way of telling if you have a locking differential or not. With a locking differential both rear wheels will turn in the same direction.

This works only if the driveshaft is free to spin. If the transmission is in park (auto) or in gear (manual) an open diff will spin the other wheel the opposite direction. A locking diff will spin the other wheel the opposite direction too except it will be harder to spin since you have to overcome the internal clutch.

With the driveshaft free the open diff will spin the other wheel opposite while the driveshaft remains stationery. A locker will usually spin the other wheel the same direction and turn the driveshaft at the same time.

I say usually because the condition of the diff and the freeness of the driveshaft to spin have a lot to do with the outcome of this test.

:) Hi, as someone who has rebuilt automatic transmissions, The parking pawl is a positive metal to metal locking mechanism. It will hold much better than a parking brake. Because of the notches in the cog wheel being spaced out, and the size of the locking pin, your vehicle will move a bit. you should always use your parking brake when on a hill / incline, or when you want to hold your vehicle exactly where you stopped, like when lining up with the trailer ball.

The rear end, or differential, does not hold your vehicle and you should not have any movement in your "U" joints. You will have some slack in the differential. (ring & pinion) Turning one rear wheel and the other one going in the opposite direction is caused by the spider gears, AKA differential, is a simple basic way of telling if you have a locking differential or not. With a locking differential both rear wheels will turn in the same direction.

Terryallan wrote:
Don't believe the movement is in the trany. I'm pretty sure it is in the U joint, and diff. After all. Once you put it in park. The trany is disengaged, and the rear end is holding the vehicle.
IF you would ever raise both rear tire off the ground with the selector in Park. You could see that IF you turn one wheel forward the other will spin backwards. It is designed so that when in park. they fight each other and keep the vehicle from rolling.

Hi Terry, you're merely observing how a differential works in an extreme case of differentiation. Here's a video that explains why you see that behavior Exngineering explained.

When placed in park, the transmission is put into "Neutral" basically and pawl is placed on one of the internal drums or gears to prevent rotation. The pawl (think of it as a single stationary gear tooth) must land in between some teeth to lock the transmission, so there will be a little movement. Then you also have the slop/play between the transmission and the wheels it is hooked to that contributes to a little movement.

Most should set the parking brake/emergency brake to take strain off of the pawl, otherwise it could fail in an extreme circumstance, such as a hill.

Terryallan wrote:
IF you would ever raise both rear tire off the ground with the selector in Park. You could see that IF you turn one wheel forward the other will spin backwards. It is designed so that when in park. they fight each other and keep the vehicle from rolling.

Ummm, that is because the driveshaft can't turn because it's locked by the transmission when it's in park...;)

DID YOU KNOW? Contrary to common thinking, the primary purpose of the transmission's "Park" position (and parking pawl) is to keep the engine's power from reaching the drive wheels when the engine is running, not to stop the vehicle from rolling when parked - this is the job of the e-brake.

http://myautomatictransmission.com/transmission-parking-pawl.htm

Terryallan wrote:
Don't believe the movement is in the trany. I'm pretty sure it is in the U joint, and diff. After all. Once you put it in park. The trany is disengaged, and the rear end is holding the vehicle.
IF you would ever raise both rear tire off the ground with the selector in Park. You could see that IF you turn one wheel forward the other will spin backwards. It is designed so that when in park. they fight each other and keep the vehicle from rolling.

:h :h :h

What high school auto mechanics class did you take???

The parking Pall locks the output shaft of the transmission, thus locking the drive line (as in it can't turn), that is why you don't roll (much anyway).