Rear axle can use any straight grade SAE 90 or SAE 140 GL-4 or GL-5 lubricant. They can also use any multi-viscosity lube. The transmissions use GL-4. SAE 90 in cooler climates and SAE 140 in warmer climates. Sta-lube GL-4 can be purchased from a local NAPA dealer in straight grades. You can also use it in the Columbia 2-speed axle.
http://www.fordbarn.com/forum/showth...t=columbia+oil