GM Full Size Vans 1987-1997 Repair Guide

Timing Chain

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REMOVAL & INSTALLATION



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

See Figure 1

  1. On some models it may be necessary to remove the grille assembly. Refer to Body & Trim for this procedure.
  2.  
  3. If necessary, remove the air cleaner assembly and the coolant recovery reservoir.
  4.  
  5. Remove the radiator, water pump, the torsional damper and the crankcase front cover. This will allow access to the timing chain.
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  7. Crank the engine until the timing marks on both sprockets are nearest each other and in line between the shaft centers.
  8.  
  9. On 1996-97 vehicles remove the crankshaft position sensor reluctor ring. On 7.4L engines tool J-41371 or its equivalent puller must be used to remove the reluctor ring.
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  11. 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.
  12.  

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.
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  3. Place the cam sprocket, with its chain mounted over it, in position on the front of the van and pull up with the three bolts that hold it to the camshaft.
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  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.
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  7. On 1987-95 models 4.3L 5.0L and 5.7L models, tighten the camshaft sprocket bolts (and nut on the 4.3L), to 21 ft. lbs. (28 Nm). On the 7.4L, tighten them to 20 ft. lbs. (26 Nm).
  8.  
  9. On 1996-97 models, tighten the camshaft sprocket bolts (and nut on the 4.3L) to 18 ft. lbs. (25 Nm). On the 7.4L, tighten them to 25 ft. lbs. (34 Nm).
  10.  

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 onto the crankshaft until it is firmly seated against the crankshaft sprocket. On 1996-97 7.4L vehicles replace the reluctor ring with a new component.
  2.  
  3. If removed, install the air cleaner assembly and the coolant recovery reservoir.
  4.  
  5. Install the front cover, torsional damper, water pump and the radiator.
  6.  
  7. If removed, install the grille assembly.
  8.  

End-play of the camshaft is zero.



Click image to see an enlarged view

Fig. Fig. 1: Timing mark alignment - 4.3L, 5.0L, 5.7L and 7.4L engines

6.2L and 6.5L Diesel Engines

See Figures 2 and 3

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



Click image to see an enlarged view

Fig. Fig. 2: Timing mark alignment - 6.2L and 6.5L engines



Click image to see an enlarged view

Fig. Fig. 3: 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. On 1987-95 models, tighten the camshaft gear bolt to 75 ft. lbs. (100 Nm). On 1996-97 models, tighten the camshaft gear bolt to 125 ft. lbs. (171 Nm).
  2.  
  3. Rotate the crankshaft 360° so that the camshaft gear and the injection pump gear are aligned as shown in the illustration (accompanying the diesel Front Cover Removal Procedure). On 1987-95 models, tighten the bolt to 17 ft. lbs. (23 Nm). On 1996-97 models, tighten the camshaft gear bolt to 20 ft. lbs. (25 Nm).
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  5. Install the front cover as previously detailed. The injection pump must be re-timed since the timing chain assembly was removed. see Fuel System for this procedure.
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