Best Gear Oil for your Deuce and a Half Transmission and Transfer case
This guide details the correct fluid selection and maintenance for the transmission and transfer case of a Deuce and a Half (M35) military truck. It emphasizes the critical need for non-detergent, straight-weight motor oil (SAE 40 recommended) or GL1 90 weight gear oil that is 'yellow metal safe' to protect internal bronze components. Using modern detergent or multi-weight oils can cause significant damage due to the lack of an oil filter in these older transmissions.











