GM Full-Size Trucks 1980-1987 Repair Guide

Drive Belts

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INSPECTION



See Figures 1, 2, 3, 4 and 5

At the interval specified in the Maintenance Intervals chart, check the water pump, alternator, power steering pump (if equipped), air conditioning compressor (if equipped) and air pump (if equipped) drive belts for proper tension. Also look for signs of wear, fraying, separation, glazing, and so on, and replace the belts as required.



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Fig. Fig. 1: There are typically 3 types of accessory drive belts found on vehicles today



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Fig. Fig. 2: An example of a healthy drive belt



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Fig. Fig. 3: Deep cracks in this belt will cause flex, building up heat that will eventually lead to belt failure



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Fig. Fig. 4: The cover of this belt is worn, exposing the critical reinforcing cords to excessive wear



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Fig. Fig. 5: Installing too wide a belt can result in serious belt wear and/or breakage

ADJUSTMENT



Belt tension should be checked with a gauge made for the purpose, while the engine is OFF. If a tension gauge is not available, tension can be checked with moderate thumb pressure applied to the belt at its longest span midway between pulleys. If the belt has a free span less than 12 inches, it should deflect approximately 1 /8- 1 /4 inch. If the span is longer than 12 inches, deflection can range between 1 /8 inch and 3 /8 inch.

See Figures 6, 7, 8, 9 and 10

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Fig. Fig. 6: A gauge is recommended, but you can check belt tension with thumb pressure



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Fig. Fig. 7: To adjust a drive belt's tension, loosen the mounting and adjusting bolts in order to allow the component to pivot



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Fig. Fig. 8: Some components and brackets, such as the AIR pump, contain square fittings in which a ratchet may be inserted and used to pivot the component



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Fig. Fig. 9: To tighten the belt on this alternator, a wooden prytool was inserted behind the housing. Once the proper tension is reached, the adjuster bolt is tightened to hold the component in place



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Fig. Fig. 10: 379 Diesel belt adjustments

REMOVAL & INSTALLATION



  1. Loosen the driven accessory's pivot and mounting bolts.
  2.  
  3. Move the accessory toward the engine until enough slack is created to remove the belt from the pulley.
  4.  

To install:
  1. Place the new belt over the pulley and move the accessory away from the engine until the tension is correct. You can use a wooden hammer handle, or broomstick, as a lever, but do not use anything metallic, such as a prybar.
  2.  
  3. Tighten the bolts and recheck the tension. If new belts have been installed, run the engine for a few minutes. With the engine OFF, recheck and readjust the belt as necessary.
  4.  

It is better to have belts too loose than too tight, because overly tight belts will lead to bearing failure, particularly in the water pump and alternator. However, loose belts place an extremely high impact load on the driven component due to the whipping action of the belt.

 
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