92 1500 Won't Shift Into 4 Wheel Drive

I have a 92 Chevy 4x4, w/350 engine. Manual shift. For some reason, it suddenly won't shift into 4 wheel drive. I got under the truck to see if the shift linkage was all hooked up and shifting fine. It is. When I shift it into 4-high or 4-low, the light by the shifter doesn't come on either, and it always has before. I've tried waiting longer, backing up, moving slowly, etc. Nothing. I'm no mechanic, so I really don't have any idea what to check for. The truck itself shifts throught the gears fine. It just seems to be 4-wheel drive specific. I'm sure I'm missing some piece of key information that would help someone diagnose my problem. Any thoughts or idea's would be most appreciated. Thanks.

You might try checking the acuator. its the thing screwed into the axle tube with wires coming out of it. this is what engages the differential. also search through some older posts on here. lots of good trouble shooting stuff. an actuator at napa is right under 40 bucks. hope this helps you.

As stated the actuator is most likely the issue. The original ones use fluid and a heater which heats the fluid. It expands and enguages the front axles. Overtime when the fluid leaks out of the actuator causing no engaugement. There is an updated actuator you can get which is mechanical versus hydraulic.

I have a 92 Chevy 4x4, w/350 engine. Manual shift. For some reason, it suddenly won't shift into 4 wheel drive. I got under the truck to see if the shift linkage was all hooked up and shifting fine. It is. When I shift it into 4-high or 4-low, the light by the shifter doesn't come on either, and it always has before. I've tried waiting longer, backing up, moving slowly, etc. Nothing. I'm no mechanic, so I really don't have any idea what to check for. The truck itself shifts throught the gears fine. It just seems to be 4-wheel drive specific. I'm sure I'm missing some piece of key information that would help someone diagnose my problem. Any thoughts or idea's would be most appreciated. Thanks.

What size and what transfer case?
As said the front Axel actuator is a problem are.
Wiring bad or shorted out.
Check for and or put 12 volts to it and see if it moves and locks in front axels.

But First check the Fuse for it.
You got to have 12 volt power to move the actuator.
Check all wiring on from front Axel actuator and transfer case.
And also the shift linkage and shift levers on transfer case.

Let us know what you find.

You won't believe what the problem was. I had the passenger side front axle replaced a while back. Apparently, the mechanic installed the axle without taking the hub off because they figured they would end up twisting of the bolts. So, to try and get that axle in, they were prying the hell out of stuff to get it in. In doing so, it actually caused a thrust washer on the inside of the 4-wheel drive housing where the pin engages the gear to slip off. When the pin was engaging, it would come up against the thrust washer. Thanks for the replies and suggestions.

You won't believe what the problem was. I had the passenger side front axle replaced a while back. Apparently, the mechanic installed the axle without taking the hub off because they figured they would end up twisting of the bolts. So, to try and get that axle in, they were prying the hell out of stuff to get it in. In doing so, it actually caused a thrust washer on the inside of the 4-wheel drive housing where the pin engages the gear to slip off. When the pin was engaging, it would come up against the thrust washer. Thanks for the replies and suggestions.
Good find and reason for it not locking in.
You are welcome and thanks for posting back the find.
Good luck with it.

As stated the actuator is most likely the issue. The original ones use fluid and a heater which heats the fluid. It expands and enguages the front axles. Overtime when the fluid leaks out of the actuator causing no engaugement. There is an updated actuator you can get which is mechanical versus hydraulic.
Hey tblake are you talking about the one that you run a cable from the differential to inside the cab. or is it one that is activated 12v?