What wheels does the parking break lock in a 4x4?

[Elan_]

What wheels does the P for Park lock in a 4x4?

Edit: I didn't mean parking break. I meant P for Park.

I had my first semi legitimate off road experience yesterday. I found a washed out path on a steep hill that led up to some water and power equipment.

When I was turning around to return back to the road I ended up getting the front driver and year passenger wheel off the ground on a mild incline. I wanted a picture of it so I put it in park but when I took my foot off the break the truck kind of lurched forward briefly but multiple times. Like P just wasn't enough to hold the truck stopped but was trying its darnedest.

It certainly didn't sound healthy and I didn't want to ruin anything so I just put it back in D and kept going. Was the torque being fully applied to only two wheels while in P overpowering something?

 

[S p a r k y]

Anytime your going to have strain on your "park" always apply the parking brake before putting in park. Will save a lot on your drivetrain. When you are ready to go back into gear, go to gear first, then release parking brake.

This doesn't answer your question, but will help that not happen again probably.

 

[mrpurplepenguin]

Shifting into P separates the transmission input shaft (connected to the engine) from the output shaft (connected to the wheels), just like N does. It also moves a locking pawl to engage the output shaft and lock it in place (once the shaft rotates so that a slot lines up with the pawl).

Even with the center diff locked (4WD mode), P wouldn't be able to hold the truck because you had a wheel off the ground on both axles. Both grounded wheels are free to spin (by just spinning the airborne wheels as well) without spinning the transmission at all, so P does nothing in that situation.

 

[Elan_]

OK that pretty much explains everything. Thanks

 

[riverwolf]

I'd recommend doing a parking brake adjustment the next time you have the rear wheels off. I'm not convinced they're adjusted that well from the factory. The factory adjustment (usually) holds under mild conditions, but I found quite a bit of room for adjustment when I checked recently. My shoes have never been driven on so my adjusments shoudln't have been to counter shoe wear.

There are stories of vehicles breaking the parking pawl when folks use that as their primary hill holder. Can't say I've ever heard of it specifically on a 4Runner, but the principle's the same...use the P-brake if you really need to hold the vehicle. I only trust "Park" on flat surfaces.