How to change thermostat on a GMC envoy with 4 wheel drive

SOURCE: 1995 GMC 2500 won't shift into 4 wheel drive,

I have a 94. Had the same problem last year. If it is the same as mine there is an actuator located on the front differential. When you pull the lever to put it in 4h this thing acts like a push rod and pushes the gears in place. It screws right in and there is a plug. I bought mine on-line for about 80 bucks. The car guy told me they do wear out becuse the get all the road grime and the part is gas filled. I'm not a mechanic but that is what I had to do.

SOURCE: Replace the thermostat on 2002 GMC Envoy

4.2L Engine the thermostat and the neck where the hose goes on is one unit $25 at autozone

1. Remove the necessary coolant from the radiator.
2. Remove the alternator, Loosen the outlet hose clamp at the thermostat housing. Remove the outlet hose from the thermostat housing.
3. Remove the thermostat housing bolts.
4. Remove the thermostat housing from the engine block.
5. Clean all of the surfaces of the thermostat housing.
6. Clean the sealing surface of the engine block.

SOURCE: My 2006 GMC Envoy Denali

MIKE,
TRY PUTTING THE TRANSMISSION INTO NEUTRAL, I HAD THE SAME EXACT PROBLEM, UNTIL I CALLED A MECHANIC FRIEND OF MINE. I COULDN'T BELIEVE HOW WELL IT WORKED.....CHECK IT OUT.

SOURCE: wont shift back from 4x4 low, to 2x2

I also have a 2002 Envoy. Shifting to and from 4wh and 4wa can be done on the fly but shifting to 4wL has to be done stoped and while in neutral. Try that. Otherwise I'm afraid its a new computer for you. Its located under the left rear seat and you need a loan for one.

SOURCE: My 2002 Gmc Envoy is stuck in 4wheel low. I

Try disconnecting the battery for a few minutes, that might get you out of trouble for now. There are some common problems with these 4wd systems. Most common is the mode position sensor on the encoder motor. Sometimes it can be the switch on the dash. Fact of the matter is I can't tell you what is wrong without using a scantool to retrieve the fault codes from the computer controlling the 4wd.