Chevrolet Repair: Oil lines, front differential, transfer case, chevy 2500hd, 4x4 truck

Question
I recently had my 2004 chevy 2500hd 4x4 truck inspected. Mechanic said oil lines needed to be replaced, and he also sail he had to drop the front differential to change the oil lines.  After I got my truck back, the truck has a hum/whine noise, in 4 wheel drive the truck bucks, and the mechanic says the transfer case may be shot.  Is there any connection between the repair they made and the new problems i have? thanks for your help.

Answer
Hi Tom, Well if this didn't happen before the repair one would think it has to be related. Transfer case maybe SHOT, not too much to go wrong inside these. I would either take it back or have someone else take a look at it. I have seen the pinions bearings go bad in the front diff, so this might be the problem. Have a second opinion first.

Sorry I can't help more

Have a Great Day                Mark