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2005 buick rainier
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Discussion Starter #1 (Edited)
I've been lucky enough to fix quite a few problems based on TrailVoy posts, but I've run into a unique situation that I haven't been able to find in the search results.

This is for a 2005 Buick Rainier with the 5.3L engine, A4WD NVG 126 transfer case and non-locking front differential. Milage is approximately 125,000, with transfer case and differential fluids changed within last 10,000 miles (long-term history unknown).

Approximately six months ago the truck seemed to be stuck in 4WD, so I replaced the transfer case encoder motor and the problem seemed to be fixed. Proper automatic transition between 4WD and 2WD.

Fast-forward to a month ago, and the same problems seemed to be happening -- stuck in 4WD at all times. I pulled the six-month-old transfer case encoder motor off and the internal gears were destroyed, just like the last one. Probably important to point out that in the six months since it was replaced, it was good weather that would have rarely required the 4WD system to engage.

I know the encoder motors are notorious for failing, but blowing two in that short time-frame suggests there is some sort of internal problem with my transfer case that is causing excessive stress on the encoder motor. Maybe the clutch lever is not always traveling smoothly? What else could be binding the encoder motor?

The truck was also driven for several months with the 4WD system engaged, which I know is asking for trouble, so I also wanted to make sure the front differential is still functioning properly before I get the transfer case issue worked out.

I put the front of the truck up on jack stands, leaving the back wheels on the ground, before I pulled the broken encoder motor off the transfer case, so the 4WD was still engaged. When I went to turn the front wheels, each one had about 20 degrees of play before stopping with a clunk, but they would not turn further than that. I tried each wheel individually, without anything preventing the opposite side from turning.

Considering the A4WD transfer case is paired with a non-locking front differential, shouldn't the front wheels have rotated in opposite directions even though the drive shaft was not able to move?

After I pulled off the broken TC encoder motor, freeing up the front drive shaft, the front wheels turned freely in opposite directions like they should (e.g. I turn the drivers-side wheel clockwise and the passenger wheel rotates counterclockwise).

Am I misunderstanding the operation of the differential on this vehicle, or is there probably something wrong with the front diff?

Thanks for any insight.
 

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2004 gmc
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26,181 Posts
My thought is like yours. You have severe problems inside your transfer case. Perhaps you have one of the older ones with the weak bearing mount inside.

Your front diff acts properly when the opposite tire spins the other way. I can't explain the other behavior you saw. It's just not consistent unless you there's a broken bit rolling around in the bottom of the diff, and it jams at times and releases the spider gears at other times.
 

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2005 buick rainier
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Discussion Starter #3
Thanks for the reply, roadie.

I'm going to teak apart the transfer case to figure out what might be causing the encoder motors to break.

And for the front differential, I'll probably have to do the same thing.
 
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