Helllo, Yes, a newbie. And now owner of a 2005 TB LT.. 4.2L 4WD. This unit has some issues and I am trying to understand how the drive train works. Given the year, it is a low miles rig, just 130,000 km (about 80,000 miles?). It has spent a lot of time sitting in storage.. My previous experience is with a '93 Cherokee - simple and easy by comparison.

Surely I am asking questions that have been asked and answered, so please direct me to the appropriate threads.

1. The rear end is a typical auto-locking GM 12-bolt, correct? I have some experience with these from pickups on the farm. Hit the gas, if a wheel slips a locking mechanism kicks in to lock the diff. Off you go, digging parallel ruts through the snow/mud. Rear end will stay locked until there is no wheel slip (le. let off the gas).
2. T-case is more or less straightforward, though different than my Jeep - as I am reading on the trusted internet. 2WD/4WD. Hi and Low ranges. In AWD, there is a mechanism to in the T-case to move power forward to the front drive when there is slippage in the rear end? New one for me. On the Jeep, the AWD (Selec-Trac) simply allowed the front diff to have left/right 'slip' (the front wheels were not locked) to minimize wear on the tires and gears on mixed surfaces - including pavement. Ignoring the TB AWD though, do the 4WD settings lock the front drive lock-step with the rear?
3. Now, the front diff.. If everything is as it should be, when engaged in 4WD (Hi or Lo), is the front end 'locked'? ie. Both front wheels will rotate at the same speed, regardless of 1) turning, 2) individual wheel traction?

My situation. As I mentioned at the outset, this unit has spent a lot of time sitting, and has hardly ever been out of the 2WD settings. I think I have 'bullied' the front wheel drive actuator to do its job. Initially, on stands, the front wheels would not engage in any of the xWD settings! The front drive shaft was engaged, but the wheels were not. What did I do? I unbolted the electronic actuator on the passenger side. Clean and greasy, and the piston moved when told to by the selector on the dash. I tried to pushing on the internal piston. It wouldn't engage with anything, even while slowly spinning the passenger front wheel by hand. The piston would move in/out a bit, and seemed to be like the clunk-clunk-clunk sound it made initially. OK. Drop the front end on the shop floor, keep the rear pumpkin lifted with a heavy duty floor-jack. Start 'er up, apply brakes, shift to neutral, shift to 4WD and wait for indicator to show shift complete, ease off the brakes. A bit of churning, a clunk, and now the rig is crawling across the shop floor! Success? Well, it now shifts in/out of xWD options. Success.

But, the front wheels are not locked to each other. The drivers side brakes are binding (another issue, to be tackled tomorrow), and when the unit is off the ground, the passenger wheel is getting all of the power. The drivers side is trying, but won't free-wheel. Is this a fault of the 'front wheel disconnect' that I am reading about? Should the front wheels by locked?

4. Do the front hubs have any sort of locking? I don't think so, but...

Anyway. Wish me luck . Lots to learn, and no more Haynes manuals to guide me. New fluids in both diffs and t-case are on the agenda next. And, get the sticking front brake to let go. Caliper, line blockage, master cylinder? Figger it out, fix it.

Thanks in advance,
Wildmustard

 

1. Unless you have a G80 RPO code on the sticker inside your glovebox door you do not have a locking rear differential. And these are 10 bolt, not 12.
2. It is NOT All Wheel Drive! It is Automatic 4 Wheel Drive, and if you value your transfer case you will never, ever use it! This setting enables the transfer case to shift itself in and out of 4WD, and it puts a tremendous amount of strain and wear on the T-case clutch packs! Do not use A4WD! If you need 4WD, then use it only as long as you need it, then switch back to 2WD. Your T-case and your bank account will both thank you.
3. The front differential does not lock, even if you have a G80 RPO code.
4. The front hubs do not have any type of locking mechanism.

 

Thank you flyboy for the quick response, and guidance.

1. The glove box sticker does include G80. Hurray. Yes, I can't count. It is 10-bolt.
2. I hear ya. It will be 2WD or 4WD only. If AWD is not recommended, is there a way to lock it out?
3. Front diff does not lock, ever. That is consistent with what I am seeing. All good.
4. Front hubs do not lock/unlock. 10-4.

Fluid changes ASAP. Lucas 75W-90 synthetic for diffs, AC Delco AutoTrak II for T-Case.

Seeing the G80 RPO code is a relief. Stuck in snow is no fun when you have one wheel spinning on ice and the other locked in snow - front and back. Now I know I can give 'er when it gets sketchy and there is hope that we'll get through.

Cheers!