GM Full-Size Trucks 1988-1998 Repair Information

Timing Chain

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REMOVAL & INSTALLATION



4.3L, 5.0L, 5.7L and 7.4L Engines

See Figures 1, 2, 3, 4, 5 and 6

  1. Remove the timing cover. This will allow access to the timing chain.
  2.  
  3. Crank the engine until the timing marks on both sprockets are nearest each other and in line between the shaft centers.
  4.  



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Fig. Fig. 1: Crank the engine until the timing marks on both sprockets are in line

  1. On 1996-98 vehicles remove the crankshaft position sensor reluctor ring, if equipped. On 7.4L engines tool J-41371 or its equivalent puller must be used to remove the reluctor ring.
  2.  
  3. Take out the bolts that hold the camshaft gear to the camshaft. This gear is a light press fit on the camshaft and will come off easily. It is located by a dowel. The chain comes off with the camshaft gear.
  4.  



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Fig. Fig. 2: Remove the camshaft gear retaining bolts



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Fig. Fig. 3: Remove the camshaft gear and timing chain

A gear puller will be required to remove the crankshaft gear.

To install:
  1. Without disturbing the position of the engine, mount the new crankshaft gear on the shaft, and mount the chain over the camshaft gear. Arrange the camshaft gear in such a way that the timing marks will line up between the shaft centers and the camshaft locating dowel will enter the dowel hole in the cam sprocket.
  2.  
  3. Place the cam sprocket, with its chain mounted over it, in position on the front of the truck and pull up with the three bolts that hold it to the camshaft.
  4.  
  5. After the gears are in place, turn the engine two full revolutions to make certain that the timing marks are in correct alignment between the shaft centers. Tighten the camshaft sprocket bolts (and nut on the 4.3L) to 21 ft. lbs. (28 Nm) on 1988-95 models. On 1996-98 models, tighten the bolts to 18 ft. Lbs. (25 Nm). On the 7.4L, tighten them to 20 ft. lbs. (26 Nm) on 1988-95 models. On 1996-98 models, tighten the bolts to 25 ft. Lbs. (34 Nm).
  6.  

When installing the crankshaft position sensor you must use install a new oil ring seal onto the sensor.

  1. Install the crankshaft position sensor reluctor ring (if equipped), onto the crankshaft until it is firmly seated against the crankshaft sprocket. On 1996-98 7.4L vehicles replace the reluctor ring with a new component.
  2.  
  3. Install the front cover, torsional damper, water pump and the radiator.
  4.  



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Fig. Fig. 4: A gear puller will be required to remove the crankshaft gear



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Fig. Fig. 5: Timing mark alignment-4.3L, 5.0L, 5.7L and 7.4L engines

6.2L and 6.5L Diesel Engines

See Figures 6 and 7

  1. Remove the front cover.
  2.  
  3. If applicable, remove the bolt and washer attaching the camshaft gear and the injection pump gear.
  4.  
  5. Crank the engine until the timing marks on both sprockets are nearest each other and in-line between the shaft centers.
  6.  



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Fig. Fig. 6: Timing mark alignment-6.2L and 6.5L engines



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Fig. Fig. 7: Timing chain installation-6.2L and 6.5L engines

  1. Remove the camshaft sprocket, timing chain and crankshaft sprocket as a unit.
  2.  

To install:
  1. Install the camshaft sprocket, timing chain and crankshaft sprocket as a unit, aligning the timing marks on the sprockets as shown in the illustration. Tighten the camshaft gear bolt to 75 ft. lbs. (100 Nm) on 1988-95 models and 125 ft. Lbs. (171 Nm) on 1996-98 models.
  2.  
  3. Install the front cover as previously detailed. The injection pump must be re-timed since the timing chain assembly was removed. See Fuel Systems for this procedure.
  4.  

 
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