Recommended Fluid
WARNING: This page does not describe the selected car, but rather 26 other vehicles, including the 1984 GMC Vandura Special, 1984 GMC Vandura, 1984 GMC Value Van, 1984 GMC Suburban, and 1984 GMC S15 Pickup. However, it is still accessible from the selected car via links, so may be relevant.
All manual transmissions except 4-speed (89 MM), 5-speed (77 MM) and those in the "S" series, use SAE 80W, GL-5 or SAE 80W-90 GL-5 multipurpose gear lubricant. The 4-speed (89 MM), 5-speed (77 MM) and all "S" series vehicles with manual transmissions use Dexron II automatic transmission fluid.