Hello,
I was plowing with my Silverado and everything was going along fine, then the 4 wheel drive just stopped working.
It's a manual shift and I still have lights on the dash. I took the actuator out and checked it.. it works..

Any help greatly appreciated.

 

For a manual shift transfer case, there’s only a few possibilities if the actuator is working.

Check the front driveshaft for broken U-joints.

If OK, drain the fluids in the front differential and transfer case. Catch them in [separate] clean containers and inspect for metal particles.

SOME metal is normal (sawdust sized grains) - what you’re looking for is larger particles, about the size of splinters and larger.

Try to use a flashlight to look inside the drain plug bores and check for larger metal pieces lying in the bottom of the cases.