Got a 1994 Chevy s10 Zr2, the 4 Lo works but the 4Hi doesn't, I can hear the transfer case activating and the actuator is good. Any suggestions whats next to try?

 

sounds like the transfer case is going out, fairly common problem is for the truck to start having issues in 2WD (usually an ear shattering reverse clunk) and then for it to just not want to move at all. your issue is slightly different but make sure that the actuator is actually pulling the front differential all the way into lock and the transfer case all the way into gear.

 

Yes the actuator is locking in, but only on 4Lo

 

have you tried disconnecting the shift cable from the transfer case, and shifting it by hand into 4 HI?

 

I've heard it could be something dealing with the TCCM? Any suggestions on that.

 

Most probably has to do with the TCCM and the electrical actuator/encoder.

One of the fault codes causes it to do this "rail to rail" shifting where it has only 2HI or 4LO.

Have to look up that thread on the issue. A lot of good information about troubleshooting and the innards on the 1st gen.

Information thread:
https://blazerforum.com/forum/tech-a...-switch-29170/

And the original repair thread with the pictures of the encoder motor.
https://blazerforum.com/forum/articl...-switch-25087/