GM S10/S15/Sonoma Pick-Ups 1982-1993 Repair Manual

Transfer Case

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FLUID RECOMMENDATIONS



When adding fluid or refilling the transfer case, use Dexron II® or the latest superceding Dexron® automatic transmission fluid for most vehicles covered by this manual. However, there are indications that some models may have been designed to run with SAE 80W or SAE 80W-90 GL5, so check your owners manual to be sure.

LEVEL CHECK



See Figure 1

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.



Click image to see an enlarged view

Fig. Fig. 1: Check the fluid level by removing the upper of the 2 plugs from the side of the transfer case

  1. If necessary for access to the filler plug, raise and support the vehicle safely using jackstands, but make sure the vehicle is level.
  2.  
  3. Remove the filler plug (upper plug of 2) from the rear-side of the transfer case.
  4.  
  5. Using your finger, check the fluid level, it should be level with the bottom of the filler hole.
  6.  
  7. If the fluid level is low, use the proper type of fluid to bring the fluid up to the proper level. Most parts stores will carry a small, hand operated pump which will greatly ease the task of adding fluid to the transfer case.
  8.  
  9. Install and tighten the filler plug.
  10.  

DRAIN AND REFILL



See Figure 2

  1. Operate the vehicle in four wheel drive in order to warm the fluid to normal operating temperature.
  2.  
  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.
  4.  
  5. Position drain pan under transfer case.
  6.  



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Fig. Fig. 2: Loosen and remove the lower plug (drain plug) in order to drain the fluid from the transfer case

  1. Remove drain and fill plugs, then drain the lubricant into the drain pan.
  2.  
  3. Install and tighten the drain plug.
  4.  
  5. Remove the drain pan and dump the fluid into a used transmission fluid storage tank, for recycling purposes.
  6.  
  7. Using Dexron II® automatic transmission fluid, fill transfer case to edge of fill plug opening.
  8.  
  9. Install and tighten the fill plug.
  10.  
  11. Remove the jackstands and carefully lower the vehicle, then check for proper operation of the transfer case.
  12.  

 
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