So I have recently purchased an 88 chevy 1500 and the 4wd does not work. the lights come on and the transfer case is fine. also the actuator in the front diff. works,I don't know what else to check for, please help me out here. The only other thing i can think of would be gears but they dont grind or make any other sounds.
Thx  

If you aren't getting power to the actuator there is a swith on the topof the transfer case that may need to be replaced but if you are getting power to it then i don't know what would cause that.  

well i've checked it out and its not that actuator, it works fine.  Anything else you can think of before I pay a shop?  

A few years ago I had the same problem after I replaced the CV shaft seals.  One of the clips on the inside had broken when re-installing the CV shaft.  Everything seemed to work fine: 4 High, 4 Lo, actuator, all worked.  After tearing apart the differential we found that the CV shaft had totally destroyed gears and other components because the splines weren't lined up correctly with the gears.  My fix.....straight axle conversion with 4-link and air bags.  I am much happier now.  If you don't want a straight axle (which I HIGHLY recommend) you'll have to have your diff torn apart and find out what's wrong.  Hopefully you know somebody that knows something about differentials or a mechanic that won't charge you much to look at it.  

Support the front of the truck on jackstands. Then remove the actuator.  Look into the actuator hole and see if you can press the shift collar in. If it won't slide in when you push on it and rotate the front driveshaft by hand, then something is causing it to bind.  I have seen one incident where the pass side axle shaft seal was replaced and the thrust washer fell down.  Then someone hammered the shaft in causing a cookie cutter effect on the thrust washer.  It ended up that the axle shaft cut a piece of the thrust washer off an it ended up jamming the shift collar.  After the thrust washer piece was removed and everything reassembled carefully it worked great.  And that was a cheap fix.  

Use a test light and see if you have power at the brown wire at the actuator and at the switch on the top of the trans case if there is no power first check the fuse in the fuse block then check if the wire is broken. If you have power then you may have to replace the switch (no big deal its about $30)