I have a 1992 automatic with electronic pushbutton 4wd. When I select 4wd low sometimes it engages but then most of the time I hear a shaft underneath that sounds like it is freespinning and then when it does engage the hubs lock with a jolt. Then when disengaging out of 4wd low it just freespins until I push the 4wd high button and then it jolts again and makes a loud noise. I don't use 4wd much. Is this just from little use or do I need repairs? Thanks.

 

Suggest that it would be easier to try exercising the shift several times. If this doesn't get things right - may have to look further into it, such as making sure all vacuum lines are intact with no leaks.

I don't have experience with the auto-locking systems, so can't offer more help. I do make it a practice to engage the 4WD about once per month to keep the diffy gears and seals lubed up.

 

could be wrong here but, the unit that switches between 2wd, 4hi & 4low is a round magnet like a starter... sometimes the magnet breaks up in the barrel it's in which cause a grinding sound when you push the selector button... you should be able to get that unit from the dealer and replace it... Its on the back of your t-case.. look for a round black barrel looking electrical box close to the rear output shaft

again i could be wrong.

good luck!

 

As I found out, the front hubs on pre-97 trucks are not vacuum-actuated, it's a clutch pack that engages when torque is applied to the front driveshaft. These clutch packs are not super durable and not for any "real" 4x4 use. Fine for a snowy driveway or slushy commute but don't expect them to hold up on rough trails or anything like that. If you ever do that, get a conversion kit to manual hubs.

Make sure the truck is slowly rolling (>5mph), shift to N, then press the button. You should hear a ratcheting noise from the front end, followed by a "clunk" once the truck slows down enough, usually around 1 or 2 mph, meaning the hubs are engaged. After the clunk put it back in drive. If you put it back in drive before the hubs lock up the front axle/diff will freewheel and usually the hubs will engage, but harshly.

Might want to check the t-case fluid. It takes a 3/8 square peg to get it out(standard size socket driver+extension works great). Take out the top peg on level ground and stick your finger in there. The fluid should either not come out, or be a slow dribble. If nothing comes out on your finger, it's low, and probably should be changed. Pull the bottom peg out, drain, and refill with 2 quarts of ATF. The t-case pumps fluid all the time, not just in 4wd.