4wd front axles unlocking

My front axles unlock and grind, usually when going from forward to reverse, or under load in 4wd, hi or low. anyone else come across this problem, and what steps can i take to fix it?

Had the same problem with my truck. the trouble was the vacume lines on the front axle which had leaks which caused the truck to engage but when strain came on it would would disengage because it was not getting the right amount of vacume. Fixed lines and it works perfect.

My thought, also.

After further inspection, its my transfer case, not my axles. its not fully engaging. Ive adjusted the shifter to make sure its going in all the way, but it still hangs sometimes. Sometimes it locks in, but usually it pops back out. Is it hosed, or is there something i might be missing?

If you're able to move the shifter as far as the transfer case will allow, then the problem is going to be internal. If this is the case it sounds like some of the engagements inside may be worn, and when you hit the right (or rather wrong) combination inside it slips out; if you hit the better (less worn) then it stays engaged.

I had my xfer case rebuilt. The shift forks were worn out, and the drive chain sloppy. cost me 400 bucks, but well worth the working 4X4, especially here in upstate NY, where we get feet of snow at a time.