4x4 Envoy Question

[pshabou]

Hi everyone I am new to the site and have come over from trailvoy.com (that forum is pretty much dead with useless help). I have heard all the experts have come here or gone to gmtnation.

My question is regarding my 2005 GMC Envoy SLT 4x4. Last winter I was driving in 4x4 (Dont remember exact setting), and all the wheels locked up and kicked the truck sideways on snow. The truck would not move. I took it off 4wheel high and put it back into 2wheel and it was OK. I continued to drive it and never messed with the 4 wheel drive option until winter was over to get it checked.

Finally this April, I have had time to fix the truck up, I love my envoy and don't want to sell it. I started with new struts, new shocks, new rear sway bar end links and bushings. The front got new upper ball joints and outer tie rods. The car has about 140k miles, and I have saved up enough cash to look into the 4 wheel drive.

I took it to 3 mechanics. 2 of the 3 told me that the front differential was shot, and 1 told me it was the transfer case, I refuse to dump money unless I really know the problem.

So I used the diagnose the 4 wheel drive diagram that you guys have provided (thanks in advance!). I flipped the switch to 4Hi, and both motors kicked on, and the lights on the switch didn't blink and stayed solid. I then jacked up the front passenger tire, The wheel spun freely, so to my knowledge this means 4x4 did not engage. I then looked under the car and the prop shaft was not spinning when i was spinning the passenger tire. I then jacked up both front tires, and when I spun the front passenger tire the drivers tire did not spin.

The conclusion was that my 4x4 disconnect was the problem. I also would like to include that whenever I spin that front passenger tire there is a noise coming from the front of the car, its not to bad, but it just sounds like something is wore out, I also hear the noise when driving slow. The Car runs and drives fine when in 2 wheel.

Before spending the money, I would just like to ask if there are any other ways to confirm or pinpoint the location? Some forums that I have read have told me that it could be more than one thing.

Thank You!!
-Paul-
(Sorry for the lengthy post, I just cant afford too much right now)

[pshabou]

I would like to add, that a couple months after the problem. I was driving to Detroit metro airport to drop off my brother. On the way home, I heard the loudest grinding noise, i pulled over thinking something was broken, i ended up driving it home. This grinding noise would come and go. Finally it came, came for a while and finally just went away (Maybe whatever was breaking, finally just broke?)

It was never in a 4 wheel setting since the snow fall last year, and this morning when following the diagnose guide.

[Trail X]

I'd start with taking the disconnect apart and evaluating it. Sure, there could be more wrong, but signs point to the disconnect.

[The Roadie]

My initial little-data diagnosis is the disconnect is now dead, but the differential preceded it. Definitely pull the diff fill plug and check the fluid condition.

What details did the mechanics give you on why they concluded what they did?

What's the fluid change history on the truck? Every 50K for the transfer case and 100K for the diffs?