I have a 92 S10 blazer with 2 button push button 4x4 which I just purchased. When I first got it, it would not shift into park. After struggling with the shift linkage, I believe it was bent, I got the gears in their proper locations.

I then replaced the vacuum actuator switch on the t-case. I pushed the 4hi button and it worked once, then it stopped working. I push it and nothing happens except when I have the transmission in reverse, then it blinks and goes out. Then the other day, it starts working again. It works perfectly all the way home in the snow. I shifted it in and out of 4hi a half dozen times. That was until I hit a speed bump. Now it won't work again. Exact same symptoms as before.

Does anyone have any ideas? I was thinking a wiring issue since it stopped working after I hit a bump.

 

that's the first place to start.

it could also be a bad encoder motor on the t-case, but i'd say it's more than likely a wiring issue.

keep us posted on your findings.

 

Wiring would be my guess as well. Check out the Tech Article (DIY) section for information on how to diagnose the NV233 transfer case. error_401 posted a pretty good thread in there and I just grabbed a fairly good run down on the 4wd system in general and put it up in that section.

 

Update-I got it to work, well sort of. First problem was the gear shift position sensor, I think is what it's called. Mounted on the steering column under the dash. It was out of adjustment, unfortunately, due to corrosion or damage, it will not stay adjusted. When I move the gearshift, it sticks and it gets knocked out of adjustment. A new one is only $10 but replacing it will be a pain given the lack of space under there. This explained why I could only shift to 4wd in reverse. The sensor was off by one whole gear.

The next problem was an encoder fault. Pulling the fuse and resetting it allows me to shift normally but only for a limited time. When it warms up, I will look for loose or dirty connections.

According to the manual, when the tccm reads so many encoder faults, it defaults into a type of safe mode. Then only by stopping, shifting to neutral, then hitting the 4hi button and finally shifting to park while it is flashing can you get 4wd. However since my gearshift position sensor was messed up, that explains why mine worked in reverse instead of neutral.