If you own one of these 1/2 to 1 ton trucks and it is 4x4, research "transfer case pump rub".
It is a known issue where the oil pump rubs a hole in the case. Once it happens, the case oil drains while driving. Burns the case up. It can be prevented and is an easy fix.

My case started making niose coming back from AZ after the New Year. Started west of Abilene. At that point it was trashed.
Spent over a week looking for a used unit. Plan on paying $1100 plus for one if you can find one local. Cores are $600 plus. I just dropped $1700 plus for one today. OEM reman.
Parts to rebuild mine totalled $1400.
My 2500HD has the same one as a 3500 truck. Not plentiful and parts are higher.