Is my AWD Escalade rearend junk?

[73TA]

My project 08 Esky with 234K miles has been pretty good so far. Took it for a 300 mile road trip and got 17 mpg on the freeway. I have been noticing a "clunk" or something like that when taking off "briskly" from a stop or a downshift when accelerating on the freeway. So I jacked it up on the rear diff and the both wheels would spin. I thought this should be impossible if it is in park.
I then got underneath it and checked the u-joints and they looked fine. Then I spun the wheels. The drive shaft was not moving, so it definitely was is park.
I then put the front wheels on concrete with the rear wheels in gravel and tried to power brake it, the rear wheels did not spin the gravel. I assume that I have been driving with only the the front diff taking all of the load and pulling the Esky instead of it being "pushed" by the rear wheels?
Are the rear "posi" clutches worn out?

I am missing something here?

Mike

Project thread

https://www.tahoeyukonforum.com/thr...-mechanic-fixed-my-blown-engine-for-7.123682/

 

[Joseph Garcia]

I can't tell you what to expect, when you try to power brake an AWD truck. Others will chime in with their thoughts.

Regarding the clunk, the slip yoke coming out of the transmission and connecting to the rear drive shaft may be the source of your clunk, coming from some play in the spline, where the slip yoke connects to the transmission. There is a nickel coated slip yoke spline that folks purchase that can eliminate the clunk, if this is the source of the clunk.

Another source of this clunk can be the 2 differential supports brackets, which have rubber bushings at both ends of the 2 support brackets, and these bushing wear, causing a clunk sound. The replacement of these 2 support brackets, along with the rubber bushings can eliminate the clunk, if this is the source of the clunk.

 

[73TA]

Just wondering why the rear end tires will spin if the driveshaft is locked in park while the rear wheels are off the ground, I now have to assume the rear end is basically "disconnected" internally in the rear diff.

Mike

 

[wjburken]

Put the thing back up on jack stands, pull the cover of the differential and see what you have going on. You could also, if you are careful, put it up on 4 jack stands so all 4 wheels are off the ground and put it in gear and see what happens. Either way, you need to pull the cover and take a look. Until you do that, you are just guessing.

 

[02Lightning]

Just wondering why the rear end tires will spin if the driveshaft is locked in park while the rear wheels are off the ground, I now have to assume the rear end is basically "disconnected" internally in the rear diff.

Mike

I think that's normal, did one wheel spin one way, and the other wheel spin the opposite? I'm not sure your applying enough torque for it to couple the front wheels.

 

[73TA]

Every vehicle that I have put on jack stands the rear wheels will not turn when it is park. That is why I assume that the rear end has some serious problems. I agree that I will need to remove the rear diff and take a look if I don't get any information that says this is normal.

Anyone want to jack up there Esky in the rear and see if this is the case?


Mike

 

[Geotrash]

Every vehicle that I have put on jack stands the rear wheels will not turn when it is park. That is why I assume that the rear end has some serious problems. I agree that I will need to remove the rear diff and take a look if I don't get any information that says this is normal.

That's true only with a true posi-traction rear end, or a locked differential. I have 2 Denali's which have the same drivetrain as yours. With the rear wheels in the air, when I spin one wheel, the one on the other side spins in the opposite direction. I know this because I was playing around with it when I changed out the rear air shocks on both of them a few months ago.

 

[gooffeyguy]

When I've had my Denali AWD up on 4 jackstands rotating the tires, I'm pretty sure I could get all 4 wheels to rotate by only turning 1 and also while in park I think. Each wheel rotated the opposite way than the one across from it.

I think it has something to do with hiw the AWD transfer case works.

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[73TA]

Thanks, great to hear that. Both tires do rotate in the opposite direction just like a standard posi does. I never tried the fronts. I guess the GM AWD transmission must lock the front wheels when in park. I guess these rigs are always in basically full time four wheel drive, unlike other vehicle manufactures that bias most of the power to the rear wheels and only activate the front wheels when traction is needed.

If that is the case, wonder how the vehicle can lock into park if all the wheels turn?

Mike

 

[gooffeyguy]

I might have had to move it into neutral when doing this, but I don't remember

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