So I have been having 4x4 issues with my 2000 4x4 blazer 4.3L. 3 button 4wd switch.

Immediately I think its a vacuum issue, but looking at the actuator, it pulls all the way in when 4x4 is engaged.

So ruling out a vac leak I think maybe the transfer case isn't engaging. So I put the truck up on jack stands. Start in 4hi and I have no rotation of the front wheels but the front driveshaft is spinning.

So I have come to the conclusion that I have a problem with the front differential internally.

I hope I am wrong.

But after reading a few other threads I realized that the front diff pulls on either side to engage the CV axles. My understanding is that these gears are probably worn or sheared.

My next step is to pull out the front diff???

 

It could be the cable. Does the 4wd light come on? The switch for the light is on the cable actuator housing at the front diff. Check the cable at the diff and make sure the shaft it pulls operate. Unhook the cable, pull the shaft and rotate the front driveshaft to see if a front tire turns. Basically try to manually engage the front diff. Sorry I can't remember the name of the shaft that cable snaps into.

 

The service 4wd light doesn't come on. I will get under and try it.