GM Full-Size Trucks 1970-1979 Repair Guide

Transfer Case

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See Figure 1



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Fig. Fig. 1: Transfer case, model 208, indicator switch, ID tag and drain and fill plug location

FLUID RECOMMENDATIONS



Conventional transfer cases require SAE 80W or SAE 80W-90 GL-5 gear lubricant; full time systems use SAE 10W-30 or 10W-40 engine oil.

LEVEL CHECKS



See Figures 2 and 3



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Fig. Fig. 2: Remove the transfer case filler plug from the rear of the transfer case



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Fig. Fig. 3: Add gear oil using a funnel or squeeze bottle

Check the four wheel drive transfer case lubricant level every 4 months or 6,000 miles.

  1. With the truck parked on a level surface, remove the filler plug from the rear of the transfer case (behind the transmission). Be careful not to take out the drain plug at the bottom.
  2.  
  3. If lubricant trickles out, there is enough. If not, carefully insert a finger and check that the level is up to the edge of the hole, EXCEPT in full time four wheel drive cases should be 1 / 2 in. below the hole.
  4.  

Lubricant may be added, if necessary, with a funnel and tube, or a squeeze bulb.

DRAIN AND REFILL



Part Time Systems

No intervals are specified for changing transfer case lubricant, but it is a good idea for trucks that are worked hard or driven in deep water.

  1. With the transfer case warmed up, park on a level surface.
  2.  
  3. Slide a pan of a least 6 pts. capacity under the case drain plug.
  4.  
  5. Remove the filler plug from the rear of the transfer case (behind the transmission). Remove the drain plug from the bottom.
  6.  
  7. Wipe the area clean and replace the drain plug.
  8.  
  9. Add lubricant with a suction gun or squeeze bulb. Conventional transfer cases require SAE 80W-90 GL-5 lubricant.
  10.  
  11. When the lubricant level is up to the bottom of the filler hole, replace the plug.
  12.  

Full Time Four Wheel Drive

The full time system requires oil changes at regular intervals, according to the amount and type of work done by the unit. Trucks used for normal on-off road work should have the transfer case oil changed at 24,000 mile intervals. When used for heavy duty work, trailer towing, snowplowing, and the like, the interval should be halved to 12,000 miles. If the truck is exposed to extremely dusty or muddy conditions, the oil should be changed at 1,000 mile intervals.

The transfer case oil must be hot before changing. Drive the truck until the engine has reached normal operating temperature, and park on a level surface.

  1. Slide a pan of at least 8 pts. capacity under the case drain plug.
  2.  
  3. Remove the filler plug.
  4.  
  5. Remove the lowest bolt from the front output shaft rear bearing retainer cover, and allow the lubricant to drain. Be careful; the oil will be hot. There may be a drain plug. If so, remove that instead.
  6.  
  7. Remove the six bolts on the left (driver's) side of the case which secure to P.T.O. (power take-off) cover. Remove this cover and allow the lubricant to drain out.
  8.  
  9. Remove the speedometer driven gear from the upper left rear corner of the case.
  10.  
  11. Use a suction gun to remove as much lubricant as possible from the case cover location and the speedometer gear location.
  12.  
  13. Install the speedometer driven gear, the P.T.O. cover, and the lowest bolt or drain plug.
  14.  
  15. Add approximately seven pints of oil through the filler plug opening. The proper oil to use is 10W-30 or 10W-40 engine oil.
  16.  
  17. Check the fluid level and add sufficient oil to raise the level to 1 / 2 in. below the filler plug opening. Replace the plug, and wipe the surfaces of the case and skid plate to remove any excess oil. Drive the truck and check for leaks.
  18.  

 
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