Ok, my friend owns a '96 Jimmy and the other night we went and had some fun in the snow (nothing too violent) and now the truck has seemed to develop an issue with the transfer case.

4WD was working perfect before except sometimes it would take a few minutes of pushing the 2HI button to get it to disengage. After having fun he pushed the 2HI button and it locked into 2HI. We drove literally 200 yards and noticed that the 4HI light was back on like it was back in 4HI. We pulled over to find out that not only was the front diff. NOT locked in, but the transfer case had locked itself back into 4HI (driveshaft is locked). We disconnected the vacuum line to the actuator and drove home after trying to get the thing back to indicating 2HI for every bit of 30 minutes.

I guess what I want to know is, has anyone ran into this issue before? Do you think something is now broken inside the tranfer case? The truck did not throw any codes that we have noticed and the crap part is that he also has a '95 Blazer 2DR that the manually shifted transfer case seems to be broken in also, but it just WON'T lock into 4WD at all.


We're stumped on the '96 GMC. We know the t-case is broken in the '95.

 

It could be the TCCM was on its way out and went the rest of the way out at that moment. BUt as for not locking the front axle in is odd, because the axle is vacuum engaged via the switch on the transfer-case.

You could always try to clean the connections on the TCCM for corrosion then go from there. Just my two cents though. Good luck, I'll definitely be paying attention to and helping out in anyway I can

 

After further testing it turns out that the front diff. is working as it should. It seems that the transfer case or the encoder motor is the culprit. At one point I hit the 2HI button and it popped right into 2HI, but when I hit 4HI again it locked and jammed into 4HI again.

As a result of this issue and him having 1 vehicle we have rigged up a (READ: temporary) way to make the vehicle driveable since we can't remove the transfercase from 4HI. We used a 2-port, electronic vaccuum switch off of an old Cadillac to modify the vaccuum signal to the front diff. actuator controlled by a toggle switch in the cab. It works great, you just have to put the truck into neutral to unlock the front differential once you turn off the switch. Ghetto fix we know, but we ran out of time and further diagnosis will take place later on in the week.