1995 Blazer 4x4 problem

New to this forum.

Hopefully someone here can give me some advice. My wife has a 95 Blazer (4.3, electronic 4x4) that she slid off the road into the ditch a couple of days ago. Just the two passenger side wheels were in the ditch. She needed to put it in 4 low to get out. Yesterday she was driving (with our 4 year old) in 4x4 on snow covered road when she heard a clunk and the truck spun in a 180. She put it into 2 wheel drive and drove it home. I took it for a drive last night and 2 wheel drive is fine but will only shft in to 4 wheel drive when stationary and then does not want to move. If you rev the engine the truck will start moving but makes a god awful noise from what sounds like the right front of the vehicle. Any suggestions?
The truck has 100,000 miles on it and has had no problem with the 4x4 before this.
I've looked at other posts on the board but can't see a similar problem.

Any advice would be appreciated.

Thanks

Having looked further at it I have a feeling it's a front differential problem. As long as the vehicle is stationary, all the 4x4 "stuff" does what it's supposed to. I noticed driving it in to the garage last night in 2 wheel drive that there is a real drag on the vehicle. I'm wondering if I've got a bad front bearing or???

What is the best way to trouble shoot the front axle. I've got a Haynes manual but doesn't describe how to trouble shoot.

Thanks,

Al T.