GM Lumina/Silhouette/Transport APVs 1990-1999 Repair Guide

Timing Chain and Gears

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The timing chain is a device used to keep the camshaft operating in synchronization with the crankshaft, and consequently, the stroke of the piston coincides with the opening and closing of the valves in their proper order. The camshaft gear is precision cut to be twice as large as the crankshaft gear. For each rotation of the camshaft gear, the crankshaft gear spins twice.

REMOVAL AND INSTALLATION



3.1L Engine

This procedure requires the use of a crankshaft sprocket removal tool, and a sprocket installation tool.

  1. Bring the engine to TDC on #1 cylinder
  2.  
  3. Disconnect the negative battery cable.
  4.  
  5. Drain and recycle the engine coolant.
  6.  
  7. Remove the right front tire and wheel.
  8.  
  9. Remove the engine front cover, as outlined in this section.
  10.  

Align the timing marks on the cam and crank sprockets. Use the alignment marks on the damper stamping or the cast alignment marks on the cylinder and case for reference.

  1. Place the #1 piston at top dead center with the marks on the camshaft and crankshaft sprockets aligned.
  2.  
  3. Unfasten the camshaft sprocket bolt, then remove the camshaft sprocket and chain.
  4.  

See Figure 1

Click image to see an enlarged view

Fig. Fig. 1: Exploded view of the timing chain and gear assemblies showing timing mark alignment.

Lock the crankshaft to prevent it from turning, by freezing it with a prybar at the flywheel before attempting to remove the crank sprocket.

  1. Remove the crankshaft sprocket using a suitable sprocket removal tool.
  2.  

To install:
  1. Install the crankshaft sprocket with a suitable tool. Lubricate the sprocket thrust surface.
  2.  
  3. Hold the camshaft sprocket with the chain hanging down and around the crank sprocket.
  4.  
  5. Align the dowel in the camshaft with the dowel hole in the camshaft sprocket.
  6.  
  7. Draw the camshaft sprocket onto the camshaft using the mounting bolts. Tighten to the specifications shown in the accompanying figure. Install the crank bolt.
  8.  
  9. Lubricate the timing chain with engine oil.
  10.  
  11. Unlock the flywheel and using a socket and breaker bar, rotate the engine (crankshaft) twice. Make sure the timing marks line up again at TDC.
  12.  
  13. Install the engine front cover, using the directions given earlier in this section, and complete the installation procedure.
  14.  
  15. Connect the negative battery cable.
  16.  

3.4L Engine

The special tools required to perform this repair procedure are a crankshaft sprocket removal tool, and a sprocket installation tool.

  1. Disconnect the negative battery cable.
  2.  
  3. Drain and recycle the engine coolant.
  4.  
  5. Remove the right front tire and wheel.
  6.  
  7. Remove the engine front cover, as outlined in this section.
  8.  
  9. Reinstall the crankshaft bolt, and using a breaker bar and socket, rotate the crankshaft until the timing marks on the crankshaft sprocket and camshaft sprocket locator hole are aligned to marks on the engine block or timing chain damper. This is the number 1 piston at top dead center.
  10.  

See Figure 2

Click image to see an enlarged view

Fig. Fig. 2: Using the special tool to remove the crankshaft sprocket

  1. Remove the camshaft sprocket bolt, then remove the camshaft sprocket and timing chain.
  2.  
  3. Remove the crankshaft sprocket by using the special tool.
  4.  
  5. Remove the timing chain damper bolts and damper.
  6.  

See Figure 3

Click image to see an enlarged view

Fig. Fig. 3: Exploded view of the timing chain and camshaft sprocket

To install:
  1. Install the crankshaft sprocket using the special tool until fully seated on the flange of the crankshaft nose.
  2.  

See Figure 4

Click image to see an enlarged view

Fig. Fig. 4: You must use a special tool to install crankshaft sprocket

  1. Apply a suitable lubricant to the sprocket thrust face.
  2.  
  3. Align the crankshaft timing mark to the timing mark on the bottom of the chain damper
  4.  
  5. Hold the camshaft sprocket with the chain hanging down and install the chain to the crankshaft gear.
  6.  
  7. Install the camshaft sprocket and timing chain. Align the timing mark on the camshaft gear (centerline of locator hole) with the timing mark on top of the chain damper. Torque the bolt to 140N.m (103lb. ft.)
  8.  
  9. Install the chain damper to the block.
  10.  
  11. Lubricate the timing chain with engine oil.
  12.  
  13. Replace the engine front cover, as outlined in this section. Use that procedure to complete installation.
  14.  
  15. Change the oil, fill the fluids.
  16.  
  17. Install the right front wheel and tighten the lug nuts.
  18.  
  19. Connect the negative battery cable.
  20.  

3.8L Engine

You will need a torque angle meter to perform this procedure.

  1. Disconnect the negative battery cable.
  2.  
  3. Drain and recycle the engine coolant.
  4.  
  5. Remove the right front wheel.
  6.  
  7. Using the procedure given earlier in this section, remove the engine front cover.
  8.  
  9. Align the timing marks on the sprockets so that they are as close together as possible.
  10.  
  11. Remove the timing chain damper.
  12.  
  13. Remove the camshaft sprocket bolt, the camshaft sprocket and timing chain, and the crankshaft sprocket.
  14.  

See Figure 5

Click image to see an enlarged view

Fig. Fig. 5: Exploded view of the timing chain and sprocket assemblies

  1. If the engine has been disturbed, or the timing marks were not aligned on tear down, begin the installation process here.
  2.  
  3. If the balance shaft timing has been disturbed, refer to the Balance Shaft procedure.
  4.  

To install:
  1. Install the crank bolt, and using a socket and breaker bar, turn the engine so that the number one piston is at TDC.
  2.  
  3. Turn the camshaft so that, with the sprocket temporarily installed, the timing mark is straight down.
  4.  

If engine has not been disturbed, and timing marks lined up on tear down, begin the repair procedure here.

  1. Assemble the timing chain onto the sprockets with the timing marks in their closest position. Put the timing mark on the crankshaft sprocket at 12 o'clock and the timing mark on the camshaft sprocket at the 6 o'clock position to line them up.
  2.  

See Figure 6

Click image to see an enlarged view

Fig. Fig. 6: Relationship of the timing marks on the cam and crank sprockets

  1. Install the timing chain and sprocket assemblies onto their respective shafts.
  2.  
  3. Install the camshaft sprocket bolt and tighten to 74 ft. lbs. (100 Nm), plus an additional 90° with a torque angle meter.
  4.  
  5. Install the timing chain damper. Tighten the bolt to 16 ft. lbs. (22Nm).
  6.  
  7. To complete the repair procedure, follow the installation directions for Timing Chain Cover, located in this section.
  8.  
  9. Connect the negative battery cable.
  10.  
  11. Install the right side wheel and tighten the lug nuts.
  12.  

 
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