I just recently purchased a 97 GMC Jimmy. The 4wd worked fine when I got it(less then two weeks ago). I put a 2"body lift with some 31" mud terrains, went to test it today and only my back tires were spinning. I then jacked up all four tires, put it in 4hi, and then in 4lo, and got nothing from either.
It is automatic 4wd. When I push the 4hi button, everything still sounds the same with the usual small electric motor shrill to engage it, yet my front tires dont spin. When I put it in 4lo, I get the usually loud clunk after rolling, but the front wheels dont cooperate in 4lo either.

What does this sound like? a driveway fix?

Sounds like you didn't reconnect the vacuum line that goes fro the t-case the the accuator under the battery.

Sounds like you didn't reconnect the vacuum line that goes fro the t-case the the accuator under the battery.

yep, my buddies 96 s10 blazer did the same but he routed his damn vacume line next to teh manifold!

The instructions for the body lift said to unbolt the vaccum canister and drill new holes, not to unplug it.
You think its something wrong with the vaccum still? If so, is there anyway to take these off and test them using battery power or something?
After you checked the vaccum line and canister, what would be your next move?

Vacuum is what controls the front axle.

Put it in 4 hi or 4 lo, leave the truck in park. see if the front drivshaft turns, it not then the t-case is in 4x4 mode and the problem lies in your vacum system. There is a vacuum hose plug on the t-case next to the front driveshaft. One hose provides vacuum from the engine to the vacuum switch. Switch is what the three hoses plugs into. One hose is a vent line and it branhes off to the front of the t-case and it typically stuns out next to the tranny dipstick tube. The last hose runs vacuum up to the actuator under the battery. If you have a hole in either the suppply hose or the actuator hose your front end wont engage.

Take the battery out, pull the cable with a pair of pliers and use a pair of vise grips to lock it in place. Now see if you have 4x4. If so, its your vacuum system. Check the hoses, check the vacum switch, and check the actuator. The test for the actuator is to push the duaphram in with your finger, then put your thumb over the bavuum hole, if the diaphram doesn't move, then its good. If it doesn hold air, it needs to be replaced.

Google Posi-Lok and never worry about it again.