S&T Series Blazer, Bravada, Envoy, Jimmy, Rainier, Trailblazer, Xtreme

Timing Chain & Sprockets

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Removal & Installation



4.2L Engine

NOTE
The following procedure requires the use of the Crankshaft Holding tool No. J-44221 and a suitable torque angle meter.

  1. Before servicing the vehicle, refer to the Precautions section.
  2.  
  3. Remove or disconnect the following:

    Camshaft cover
     
    Timing chain (front) cover
     
    Tension on the timing chain by moving the tensioner shoe in. Place a tee into the tension to hold the shoe in place.
     
    Top chain guide bolts and guide
     
    Exhaust camshaft position actuator bolt and actuator
     
    Intake camshaft sprocket bolt and sprocket
     
    Timing chain
     
    Crankshaft sprocket
     
    Cylinder head access hole plugs
     
    Timing chain tensioner shoe bolt and shoe
     
    Timing chain tensioner guide bolts and guide
     
    Timing chain tensioner bolts and tensioner
     

  4.  

To install:


NOTE
Every seventh link of the timing chain is darkened to help in aligning the timing marks.

  1. Install or connect the following:

    Timing chain tensioner and bolts. Tighten to 18 ft. lbs. (25 Nm).
     
    Timing chain guide and bolts. Tighten to 89 inch lbs. (10 Nm).
     
    Timing chain tensioner shoe and bolt. Tighten to 19 ft. lbs. (26 Nm).
     
    Cylinder head access hole plugs and tighten to 44 inch lbs. (5 Nm)
     
    Crankshaft Holding tool No. J-44221, or equivalent with the camshaft flats up and the No. 1 cylinder at Top Dead Center (TDC)

    Click image to see an enlarged view

    Fig. Proper installation of the crankshaft holding tool with the No. 1 cylinder at TDC

     
    Crankshaft sprocket
     
    Intake camshaft sprocket into the timing chain
     

  2.  
  3. Align the dark link of the timing chain with the timing mark on the intake camshaft sprocket.Feed the timing chain down through the opening in the head.
    NOTE
    It may be necessary to remove the crankshaft holding tool to rotate and hold the camshaft hex to align the pin to the camshaft sprocket


    NOTE
    It may be necessary to remove the crankshaft holding tool to rotate and hold the camshaft hex to align the pin to the camshaft sprocket


    NOTE
    Rotate the camshaft actuator clockwise relative to the camshaft prior to tightening the bolt.



    Timing chain onto the crankshaft sprocket. Align the dark link of the timing chain with the timing mark on the crankshaft sprocket.
     



    Intake camshaft sprocket onto the intake camshaft
     
    Intake camshaft washer and bolt
     
    Exhaust camshaft actuator into the timing chain. Align the dark link of the timing chain with the timing mark on the exhaust camshaft actuator.
     



    Exhaust camshaft actuator onto the exhaust camshaft
     

  4.  
  5. Rotate the camshaft actuator clockwise (as seen from the front of the vehicle).
    WARNING
    The camshaft actuator must be fully advanced during installation. Engine damage may occur if the camshaft actuator is not fully advanced.



    Click image to see an enlarged view

    Fig. Rotate the camshaft actuator clockwise

  6.  
  7. Install the exhaust camshaft actuator bolt and tighten to 18 ft. lbs. (25 Nm), plus an additional 135 degrees, using a torque angle meter.
  8.  
  9. Tighten the intake camshaft sprocket bolt to 22 ft. lbs. (30 Nm), plus an additional 135 degrees, using a torque angle meter.
  10.  
  11. Remove the tee from the timing chain tensioner to regain tension on the timing chain.
  12.  
  13. Remove the crankshaft holding tool. The dark lines on the timing chain should be aligned with the marks on the sprockets.

    Click image to see an enlarged view

    Fig. The dark lines on the timing chain should be aligned with the marks on the sprockets

  14.  
  15. Install or connect the following:

    Top chain guide
     
    Suitable threadlock to the top chain guide bolt threads, then install and tighten to 89 inch lbs. (10 Nm)
     
    Engine front cover
     
    Camshaft cover
     

  16.  

4.3L Engine

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

  1. Before servicing the vehicle, refer to the Precautions section.
  2.  
  3. Remove the timing cover from the engine.
  4.  
  5. Rotate the crankshaft until the No. 4 cylinder is on the Top Dead Center (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.
  6.  
  7. Remove or disconnect the following:
    NOTE
    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.



    Crankshaft Position (CKP) sensor reluctor ring, if equipped

    Click image to see an enlarged view

    Fig. Timing mark alignment

     
    Camshaft sprocket (along with the timing chain). If the sprocket is difficult to remove, use a plastic mallet to bump the sprocket from the camshaft.
     

  8.  
  9. If necessary use J-5825-A crankshaft sprocket removal tool to free the timing sprocket from the crankshaft.
  10.  
  11. If necessary, remove the crankshaft sprocket key.
  12.  

To install:

  1. Inspect the timing chain and the timing sprockets for wear or damage, replace the damaged parts as necessary.

    Click image to see an enlarged view

    Fig. Removal (top) and installation of the crankshaft timing gear

  2.  
  3. Using a putty knife, clean the gasket mounting surfaces. Using solvent, clean the oil and grease from the gasket mounting surfaces.
  4.  
  5. Install or connect the following:
    NOTE
    During installation, coat the thrust surfaces lightly with Molykote® or an equivalent pre-lube.



    Crankshaft sprocket key, if removed
     
    Crankshaft sprocket onto the crankshaft using J-5590 crankshaft sprocket installation tool and a hammer without disturbing the position of the engine
     



    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.
     
    Timing chain under the crankshaft sprocket, then place the cam sprocket, with the chain still mounted over it, in position on the front of the camshaft
     
    Camshaft sprocket-to-camshaft retainers to 18 ft. lbs. (25 Nm)
     

  6.  
  7. 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.

    CKP sensor reluctor ring, if equipped
     
    Timing cover
     

  8.  

5.3L Engine
  1. Before servicing the vehicle, refer to the Precautions section.
  2.  
  3. Remove the oil pump.
  4.  
  5. Rotate the crankshaft until the timing marks on the crankshaft and the camshaft sprockets are aligned.
    WARNING
    Do NOT turn the crankshaft after the timing chain has been removed to prevent damage to the pistons and valves.

  6.  
  7. Remove or disconnect the following:

    Camshaft sprocket bolts
     
    Camshaft sprocket and timing chain
     
    Crankshaft sprocket using Pulley Puller No. J 8433, Crankshaft End Protector Tool No. J 41816-2 and Crankshaft Sprocket Removal Tool No. J 41558

    Click image to see an enlarged view

    Fig. Use the proper tools to remove the crankshaft sprocket-5.3L engine

     
    Crankshaft sprocket key, if necessary
     

  8.  
  9. Clean and inspect the timing chain and sprockets.
  10.  

To install:

  1. Install or connect the following:
    NOTE
    Properly locate the camshaft sprocket locating pin with the cam sprocket alignment hole. The sprocket teeth and timing chain must mesh. The camshaft and crankshaft sprocket alignment marks MUST be aligned properly. Locate the camshaft sprocket alignment mark in the 6 o-clock position. It may be necessary to rotate the camshaft or crankshaft to align the marks.



    Key into the crankshaft keyway, if removed. Tap the key into the keyway until both ends of the key bottom into the crankshaft.
     
    Crankshaft sprocket onto the front of the crankshaft. Align the crankshaft key with the sprocket keyway.
     
    Crankshaft sprocket using Sprocket Installation Tool No. J 41665. Install the sprocket onto the crankshaft until fully seated against the crankshaft flange. Rotate the crankshaft sprocket until the alignment mark is in the 12 o-clock position.

    Click image to see an enlarged view

    Fig. Crankshaft sprocket installation-5.3L engine

     



    Camshaft sprocket and timing chain

    Click image to see an enlarged view

    Fig. Proper alignment of the timing marks for timing chain installation-5.3L engine

     
    Camshaft sprocket bolts and tighten to 26 ft. lbs. (35 Nm)
     
    Oil pump
     

  2.  

 
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