Recommended Fluid
WARNING: This page does not describe the selected car, but rather 28 other vehicles, including the 1985 GMC Vandura Special, 1985 GMC Vandura, 1985 GMC Value Van, 1985 GMC Suburban, and 1985 GMC Safari. However, it is still accessible from the selected car via links, so may be relevant.
All manual transmissions except 4-speed (89mm), 5-speed (77mm) and those in the "S" series, use SAE 80W, GL-5 or SAE 80W-90 GL-5 multipurpose gear lubricant. The 4-speed (89mm), 5-speed (77mm) and all "S" series vehicles with manual transmissions use Dexron II automatic transmission fluid.