Chevy four wheel drive problem

I have a 2001 Chevy Silverado 1500HD that will not engage into four wheel drive. I would like to avoid giving the stealership $100 just for diagnostics. I would also like to avoid throwing parts at it in an attempt to fix the problem. I know the actuators commonly go out. How can I verify that they work or not?

The symptoms:

I press the 4hi button (yes the dreaded push button chevy 4x4). It blinks a few times and stays solid like normal. I can hear a whirring at the transfer case and at the front axle. The front tires will not break traction (this is on a snowy road).

I press the 4lo button. Whirring at the t case, kind of a clunk at the front axle. Again, front tires will not break traction.

I press 4auto. After a while, the service 4x4 light comes on. I do not get this light when using 4hi or lo.

The 4x4 worked great when I bought this truck a few months ago. I checked the t case fluid the other day while trying to figure this out, it is pitch black and stinks. I have lots of experience with t case fluids from working in a quick lube, this smell was not normal.

Any ideas?


Have it scanned for codes and post them here. Not the description but the actual code number.