GM Full-Size Trucks 1988-1998 Repair Information

Manual Transmission

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FLUID RECOMMENDATION





Muncie 117mm: API GL-5, SAE 80W-90
 
Getrag 85mm: Syncromesh Transmission Fluid
 
NVG 4500: Castrol Syntorq GL-4
 
NVG 5LM60: Syncromesh Transmission Fluid
 
NVG 3500: Syncromesh Transmission Fluid
 

FLUID LEVEL CHECK



See Figure 1

Check the lubricant level at least twice a year, even more frequently if driven in deep water.

  1. With the truck parked on a level surface, remove the filler plug from the side of the transmission case. Be careful not to take out the drain plug at the bottom.
  2.  
  3. If lubricant begins to trickle out of the hole, there is enough. If not, carefully insert a finger (watch out for sharp threads) and check that the level is up to the edge of the hole.
  4.  
  5. If not, add sufficient lubricant with a funnel and tube, or a squeeze bulb to bring it to the proper level. You can also use a common kitchen baster.
  6.  
  7. Install the plug and tighten to 17 ft. lbs. (23 Nm) on the Muncie and Getrag; 30 ft. lbs. (40 Nm) on NVG 4500; and 44 ft. lbs. (60 Nm) on the NVG 5LM60. Road test the truck and check for any leaks.
  8.  



Click image to see an enlarged view

Fig. Fig. 1: Use your finger to check the oil level in the manual transmission

DRAIN AND REFILL



No intervals are specified for changing the transmission lubricant, but it is a good idea on a used vehicle, one that has been worked hard, or one driven in deep water. The vehicle should be on a level surface and the lubricant should be at operating temperature.

  1. Position the truck on a level surface.
  2.  
  3. Place a pan of sufficient capacity under the transmission drain plug.
  4.  
  5. Remove the upper (fill) plug to provide a vent opening.
  6.  
  7. Remove the lower (drain) plug and let the lubricant drain out.
  8.  


CAUTION
The oil will be hot! Be careful when you remove the plug or you'll be taking a bath in hot gear oil.

  1. Install the drain plug and tighten to 17 ft. lbs. (23 Nm) on the Muncie and Getrag; 30 ft. lbs. (40 Nm) on NVG 4500; and 44 ft. lbs. (60 Nm) on the NVG 5LM60.
  2.  
  3. Add lubricant with a suction gun or squeeze bulb.
  4.  
  5. Reinstall the filler plug. Run the engine and check for leaks.
  6.  

 
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