For the past two months, it has been increasingly snowier where I live and 4wd has become more necessary for daily commute, but when the weather drops below freezing my 4 high and 4 low do not spin the front wheels. 4 auto works fine though. The switches for 4wd do act like they are working fine, and you can still hear the transfer case shifting in and out of 4wd but the front wheels will not spin. I had the 4wd tested by a mechanic and they said it worked fine, but still won't work if the temperature outside goes below freezing. Any ideas on what might be causing this problem?

 

If it's an old actuator, you might have the issue when cold. but not warmer. I get a new actuator for the front axle. Put some sealer on the treads to keep stuff out and use dielectric grease on the plug-in wires to keep moisture out.

 

Since my last post, I managed to get my Tahoe into 4wd, but now it will not shift out. When you click on 2 high it will say it in two high, but act like the transmission is in neutral. When you put it back in 4 high it makes a clunk and works fine again. Would this still be the front diff actuator?