Unable to get into 4WD Low

[PEIslander]

My 94 Chevy 3500 has a new "issue". On the weekend we were pulling downed trees and I was doing so in 4WD Low. While pulling a tree (likely about 2000 lb) I heard a bit of a bang and the truck wouldn't move. I shut off the truck and restarted, placed the trans in Neutral and tried to re-engage 4WD Low. When I attempt this I hear nasty grinding. I get grinding also trying to put the truck into 2wd or 4wd high (trans in neutral) however I can engage 2wd and 4wd high if I shut down the engine first. Any suggestions on what may be broken? This truck has the Borg Warner 4401 Transfer Case.
Thanks

 

[Schurkey]

The other, lighter-duty transfer cases have a habit of wearing-out the plastic pads on the shift forks, leading to partial gear engagement. They they "pop out of gear". There's also a snap-ring that breaks leading to problems with the "encoder motor" getting into the various ranges.

No idea on the B-W heavy-duty unit.