97 Ram transfer case help

So I just bought this 97 Ram 1500 4x4. It has/had a plethora of problems. After putting on new front wheel hubs, U-joints, axel seals, all new brakes, rotors master, drums. Exhaust (had no muffler) The list goes on. After doing all that and much more finally drive it, it has a wierd noise coming from the drivetrain that I think is the transfer case. Sounds like something is rubbing howling metal on metal rubbing. Sounds similar to a harley primary sprocket, but louder. Only does it when driving. 4wd works and did not notice it as loud in 2wd, but also did not go that fast either.
The book calls for ATF in the case, but in my harley I ran 20w50 to quiet it down. Can I do the same for the transfer case in this truck? I don't think it is a driveshaft U-joint but can they squeal without them shaking? The truck has no driveline/brake vibrations at all. I just can't figure out this noise. Any suggestions???