1978 Chevy Truck

Drive Train Axles Bearings problem
1978 Chevy Truck V8 Four Wheel Drive Automatic

hey,
I have a 1978 chevy k-20, I hade it in the field when the transmission just quits and it revs up and doesnt move. After an hour it runs but when its in netrual you can hear a grinding noise in the transfer case and the truck only goes in reverse. I think its the transfer case, any info will be helpful.
Donnie