1999 gmc jimmy 4x4


having trouble with the front axle disengaging also have trouble lite that says service 4wd i’ve changed fluids in the axle and transfer case.looking at a chiltons book i see this thermal actuator could that be gummed up,wore out or being that its push button control electrical? Or is there a part that normally goes bad


The transfer case on my 2000 Blazer has trouble engaging 4wd, unless I use it once a week or so. A GM tech told me that the control module (in the right kick panel) tends to freeze/lock up if not used on a regular basis. I always thought the problem was with the actuator motor on the transfer case. He recommended unplugging it to reset the module. I don’t feel like removing the panel so I just disconnect the battery to reset it. This also takes care of the 4wd Service light.

I have found it helps to be moving slowing when I switch to 4wd Hi. If all else fails I disconnect the battery. Since I’ve been making a point to switch to 4wd once a week, the truck has been behaving.

Good luck,

Ed B.


hey there i went around to a couple of shops and the gm parts man said if it was the unit on the transfer it would cost 573.00 if it was the axle servo 132.00 So i stopped at a service garage and he said ,oh yeah generally it is a electrical vaccumn unit ( i have’nt looked for it yet )but i thought he said on top of the transfer case that has a check ball in it that jams and it runs about 90.00 i’m going to look into it tomorrow,but right now the wife is going to try it since i disconnected the batt. i’ll let ya know