So I can’t find anything with this exact issue. My 06 H3 (131,000 miles) is acting up in what I assume the 4WD area. Basically, randomly, when turning it will “bite” like it’s in 4WD, but at other times it won’t. I’ve read into the plastic shift fork, and I had one shop check it out, they said the fork is shifting just fine. I’m going to another shop Tuesday, but figured I’d check here first. I just had the transmission rebuilt less than 1,000 miles ago and they drained and replaced the transfer case fluid. That shop thinks it’s an electrical issue since there’s no consistency to it.

It did it literally nonstop when I first bought the car (About 127,000 miles), and the tires had a .5 inch difference in tread from front to back, so I put new tires on and it stopped for awhile. But it’s since been acting up again.

The last thing, is every once and awhile I will hear a big “CLUNK” almost like I hit a huge bump, enough to make me jump every time, and it usually fixes after that. But that’s usually when I’m going slow, like 5-8mph and turning out of a parking lot

Does anybody have any ideas?

 

How did the know the "fork was shifting just fine"? Did the use the Xray vison goggles and watch it?

Did they know that the 2006 T Case needs additional fluid added in from the speed sensor to get it to the proper full level?
GM Bulletin: "For all 2006 Model Year Vehicles and for 2007 model year vehicles if the VIN is 56TDN13E778100102 or prior:
Remove the speed sensor connector (top rear of t/case), then remove the speed sensor.
Add 250 ml (8.45 oz) of fluid through the speed sensor hole.
Install the speed sensor and tighten to 13 lb ft or 17 N·m. Then install the speed sensor connector to the speed sensor.
This additional fluid is needed."

You can do the obvious for a 16 year old vehicle(electrical connections deteriorate over time), get under it, unplug the T Case Actuator connector, clean both ends with CRC Electronics Cleaner, let dry and reconnect. That is easy, easy stuff first is what Grandad always said.

 

Did they pull the tcase apart to "check it out"?

Either you have a front diff CV shaft issue where the cage has wallowed out and the ball bearings get stuck in a certain position then "pop" back to free or it is the Tcase.
Sounds to me more like your Tcase in sticking in 4HI LOCK. Which is a worn shift fork (internal) issue.


Did you put it in 4HI LOCK, pull the front prop shaft (chock the tires before removing the shaft) drive it and see if the binding is still present. If it is, then it's on the differential side. If not, then it is Tcase related.

 

It was the t-case shift fork. Last time I go to that shop

I opened the t-case myself, replaced the torn up plastic one with the doorman metal one and haven’t had an issue since!

 

Good job. Sometimes (seems more often lately) when you want something done right, you have to do it yourself.