GM Astro/Safari 1985-1996 Repair Guide

Transfer Case



When adding fluid to the transfer case, use Dexron®II (or the latest superceding) automatic transmission fluid for 1985-95 models or Dexron®III for 1996 models. The newer Dexron®III us the supersedes Dexron®II and may be used in all transfer cases covered by this guide. Inspect the transfer case level at your first oil change, then at every other oil change.


See Figure 1

Click image to see an enlarged view

Fig. Fig. 1: Transfer case fluid plugs

The fluid level should be checked at least annually and more often if any leakage or seepage is observed.

When checking the fluid, the vehicle must be level. If it was necessary to raise and support the vehicle to access the filler plug, the vehicle must be supported at sufficient points (all wheels or 4 points on the frame) so it is sitting level and is not tilted forward/backward or to one side.

  1. If necessary for access to the filler plug, raise and support the vehicle safely using jackstands, but make sure the vehicle is level.
  3. Remove the filler plug (upper plug of the 2) from the rear-side of the transfer case.
  5. Using your finger, check the fluid level, it should be level with the bottom of the filler hole.

Watch for sharp threads in the filler plug opening. When present, they can give you a nasty cut.

  1. If the fluid level is low, add fluid to bring the level up to the filler hole. Most parts stores will carry a small, hand operated pump which will greatly ease the task of adding fluid to the transfer case.
  3. Install and tighten the filler plug.


See Figure 1

Under normal conditions, the transfer case fluid should not need to be changed. However, if you purchase a used vehicle, it is usually a good idea to get a clean start with all of the fluids. Also, if the vehicle is operated in high water (up to the level of the transmission) it is definitely a good idea to change the fluid.

  1. Operate the vehicle in 4 wheel drive in order to warm the fluid to normal operating temperature.
  3. If necessary for access to the drain and filler plugs, raise and support the vehicle safely using jackstands. Support the truck so it is level; this is necessary to assure the proper fluid level is maintained when the case is refilled.
  5. Position drain pan under transfer case.
  7. Remove drain and fill plugs, then drain the lubricant into the drain pan.
  9. Install and tighten the drain plug.
  11. Remove the drain pan and dump the fluid into a used transmission fluid storage tank, for recycling purposes.
  13. Fill transfer case to the edge of fill plug opening. Refer to the fluid recommendations found earlier in this section to determine the proper type of fluid.
  15. Install and tighten the fill plug.
  17. Remove the jackstands and carefully lower the vehicle, then check for proper operation of the transfer case.