What kind of oil and what is the oil capacity for a 1991 Chevrolet 2500 transfer case?

Go Here >http://www.amsoil.com/scripts/runisa.dll?amsoiloaf:index< to look up your Truck since your Engine is not listed in the question 2500 HD or 2500 LD, Diesel or Gas. As to the Gear Oil to use, I suggest Synthetic Gear Lube SAE 80W-90 (AGL) from AMSOIL. Hope This Helps.