GM Astro/Safari 1985-1996 Repair Guide

Timing Chain

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REMOVAL & INSTALLATION



4.3L Engine

See Figures 1, 2, 3, 4, 5, 6, 7 and 8



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Fig. Fig. 1: Exploded view of a typical 4.3L engine timing chain and gear assembly-use of studs may vary



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Fig. Fig. 2: Align the timing marks closest together (No. 4 TDC) before starting-NOTE that No. 1 TDC would be aligned, but with both timing marks at top of their travel



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Fig. Fig. 3: Remove the timing cover, then turn the crankshaft as necessary to align the timing marks



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Fig. Fig. 4: Loosen and remove the camshaft sprocket retaining bolts ...



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Fig. Fig. 5: ... then remove the camshaft sprocket along with the timing chain



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Fig. Fig. 6: If necessary, use a suitable puller to remove the crankshaft sprocket



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Fig. Fig. 7: GM crankshaft sprocket removal tool



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Fig. Fig. 8: Use the GM installation tool (or a suitable driver) to install the crankshaft sprocket

The 4.3L engine is the only engine covered by this guide which uses a timing chain and gear (sprocket) assembly to turn the camshaft. The 2.5L engine uses a direct gear drive (without a chain).

The following procedure requires the use of the Crankshaft Sprocket Removal tool No. J-5825-A or equivalent, and the Crankshaft Sprocket Installation tool No. J-5590 or equivalent.

  1. Remove the timing cover from the engine.
  2.  
  3. Rotate the crankshaft until the No. 4 cylinder is on the TDC of its compression stroke and the camshaft sprocket mark aligns with the mark on the crankshaft sprocket (facing each other at a point closest together in their travel) and in line with the shaft centers.
  4.  
  5. For 1996 models, remove the crankshaft position sensor reluctor ring from the end of the crankshaft.
  6.  
  7. Remove the camshaft sprocket-to-camshaft nut and/or bolts, then remove the camshaft sprocket (and balance shaft drive gear on VIN W engines) along with the timing chain. If the sprocket is difficult to remove, use a plastic mallet to bump the sprocket from the camshaft.
  8.  

The camshaft sprocket (located by a dowel) is lightly pressed onto the camshaft and should come off easily. The chain comes off with the camshaft sprocket.

  1. If necessary use J-5825-A or an equivalent crankshaft sprocket removal tool to free the timing sprocket from the crankshaft.
  2.  

To install:
  1. Inspect the timing chain and the timing sprockets for wear or damage, replace the damaged parts as necessary.
  2.  
  3. If removed, use J-5590, or an equivalent crankshaft sprocket installation tool and a hammer to drive the crankshaft sprocket onto the crankshaft, without disturbing the position of the engine.
  4.  
  5. On VIN W engines, align and install the balance shaft drive gear. For details, please refer to the balance shaft procedure found later in this section.
  6.  

During installation, coat the thrust surfaces lightly with Molykote® or an equivalent pre-lube.

  1. Position the timing chain over the camshaft sprocket. Arrange the camshaft sprocket in such a way that the timing marks will align between the shaft centers and the camshaft locating dowel will enter the dowel hole in the cam sprocket.
  2.  
  3. Position the chain under the crankshaft sprocket, then place the cam sprocket (on VIN W motors the balance shaft drive gear must still be in place), with the chain still mounted over it, in position on the front of the camshaft. Install and tighten the camshaft sprocket-to-camshaft retainers to 21 ft. lbs. (28 Nm).
  4.  
  5. With the timing chain installed, turn the crankshaft two complete revolutions, then check to make certain that the timing marks are in correct alignment between the shaft centers.
  6.  
  7. For 1996 models, install the crankshaft position reluctor ring to the end of the shaft.
  8.  
  9. Install the timing cover.
  10.  

 
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