I have a 96 Sierra Z71 Extended Cab and have the push button 4 wheel drive. When I am in 2HI the "4 HI" button is solid. When I try switching to either 4HI or 4LO I will hear a "clunking" sound like it is engaging and then the corresponding button with remain blinking indefinitely and never turn solid. Now although it seems like it is changing into 4 wheel drive, it is not. It will get really torqey like it does in 4LO but only the back wheels move. I have tried replacing the actuator (it was a second hand one) and that did not work. Now I am really lost as to where to go next. I tried searching the forums here but no really solid answers on what I may try next. Please help me here I am getting stuck in the snow everyday and it sucks really bad. Thank you very much.

Daniel

The easiest way of telling if the transfer case is engaged is to turn the front driveshaft by hand. When it is in 2wd it should turn free. In 4hi or 4lo the driveshaft should be locked. If it is not then the problem is with the transfer case. If the driveshaft is locked then the problem is the front actuator or power going to it.

Do you know if you have the thermal actuator or the motor driven actuator?

James

How can I tell which actuator I have? Also I am in Wyoming so cold weather is an issue. I read about issues with the actuators and cold.

The motor driven actuator has three wires connected to it. Black is ground, Blue is 12v+ when in 4wd, brown is continous 12v+. There is another connector that goes to the switch that tells the lights that the 4wd is engaged and I don't remember but I think it had 2 wires and is located closer to the axle housing.

The thermal actuator came on the 96 models and it had two wires in the connector, Blue and Black. The brown wire on the motor driven actuator is added as part of the upgrade wiring harness. If your still has the thermal actuator, I highly recommend upgrading it.

Looking at the wiring diagram, it looks like the switch wires are Blue and Black/white stripe.

James

I have a 96 Sierra Z71 Extended Cab and have the push button 4 wheel drive. When I am in 2HI the "4 HI" button is solid. When I try switching to either 4HI or 4LO I will hear a "clunking" sound like it is engaging and then the corresponding button with remain blinking indefinitely and never turn solid. Now although it seems like it is changing into 4 wheel drive, it is not. It will get really torqey like it does in 4LO but only the back wheels move. I have tried replacing the actuator (it was a second hand one) and that did not work. Now I am really lost as to where to go next. I tried searching the forums here but no really solid answers on what I may try next. Please help me here I am getting stuck in the snow everyday and it sucks really bad. Thank you very much.

Daniel
Re-lube NOW & every 2 years...always...it will fix your problem.

OK, relube what?
thanks,
Bob B

Lube the transfer case..the linkage and gears are most likely dry.

i had the same problem with my electronic 4x4. it turned out to be a vacuum hose had simply fallen off. i just reconnected it and instant fix. have you checked into this as a possibity?

spankenchek

i had the same problem with my electronic 4x4. it turned out to be a vacuum hose had simply fallen off. i just reconnected it and instant fix. have you checked into this as a possibity?

spankenchek

S10 trucks use vacuum for the front actuator. I don't know of any full size trucks that do. The 96 1/2 ton came with the thermal actuator but many have been upgraded to the motor driven actuator.

James

I wound up selling the truck with the problem still there. Thanks for everyones help.