Recommended Fluid
WARNING: This page does not describe the selected car, but rather 28 other vehicles, including the 1986 GMC Vandura Special, 1986 GMC Vandura, 1986 GMC Value Van, 1986 GMC Suburban, and 1986 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.