Where does 4wd disengage? Any help?

Both!

Usually you have to be slightly moving to fully engage both the iffy electronic engaging t-case and the engagement gear in the front drive. The light blinking usually means it isn't slipping into place and after a few seconds it aborts the attempt and stays in 2wd.

As for the front driveshaft spinning in 2wd...are you talking going down the road its spinning or at a stand still you can/cant spin it by hand?

The actuator is the piece that I know of that needs replacement most often. The electric motor that is used to engage/disengage the transfer case is also a weak link.

Truck OFF in Park in 2 wheel yes the shaft will spin by hand

to check differential engagement

Truck in 4x4 start truck move truck a few feet put truck in PARK Block the BACK WHEELS Raise one of the Front wheels ( left side for ease) turn Wheel by hand Front Driveshaft should move , If Not that Switch isnot engaging Front Axles . I'm trying to

Full size it is probably a bad actuator on the front axle. The older ones were just a wax pellet type that heated up and moved the engagement pawl. Replace it with the newer motor driven unit and you should see a BIG difference.

S-Series uses a vacuum actuator and cable to pull the lever.

It is a full size k series. big block Thanks !

Thanks! I will try these tests this weekend.

This is why I like my 2 wheel drive truck because I never have any of these problems.

When they make a 2 wheel drive that goes in snow and mud like a 4 wheel drive I'll buy it.

Brian

No U Have different Problems ..

I always carry lots of weight in the back and if I put chains on the wheels it goes more places than 4 wheel drive trucks.

What are you smoking?