GM Lumina/Grand Prix/Cutlass Supreme/Regal 1988-1996

Balance Shaft

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REMOVAL & INSTALLATION



2.5L Engine

See Figure 1



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Fig. Fig. 1: Exploded view of the force balancer assembly, used on 2.5L engines

The 2.5L engine uses a force balancer assembly that is driven directly from the crankshaft. Two eccentrically weighted shafts and gears are counter rotated by a concentric gear on the crankshaft at twice the crankshaft speed. The balancer helps dampen engine vibration and includes a sump pickup screen, a gerotor-type oil pump and an oil filter. The filter is serviced through an opening in the bottom of the oil pan.

  1. Disconnect the negative battery cable.
  2.  
  3. Raise and safely support the vehicle.
  4.  
  5. Drain the engine oil into a suitable container, then remove the oil filter assembly.
  6.  
  7. Remove the oil pan assembly, as outlined earlier in this section.
  8.  

When installing the balancer, the end of the housing without the dowel pins MUST remain in contact with the block surface. If it loses contact, gear engagement may be lost and permanent damage to either the crank or balancer gears may result.

  1. Unfasten the four force balancer attaching bolts and remove the balancer assembly. Refer to the accompanying force balancer illustration in this section.
  2.  

To install:
  1. Rotate the engine to Top Dead Center (TDC) on the No. 1 and No. 4 cylinders.
  2.  
  3. Position the balancer assembly onto the crankshaft with the balancer weights at BDC (bottom dead center), plus or minus one half of a gear tooth.
  4.  
  5. Tighten the bolts in the following sequence in two steps, 3-1-2-4.
  6.  
  7. The first torque step to 107 inch lbs. (12 Nm). The second torque step to 11 ft. lbs. (15 Nm) plus 75° (1 flat) for the short bolts and 11 ft. lbs. (15 Nm) plus 90° (1 1 / 2 flats) for the long bolts.
  8.  
  9. Install the oil pan assembly as outlined earlier in this section.
  10.  
  11. Carefully lower the vehicle.
  12.  
  13. Refill the crankcase with the specified amount and type of engine oil. Start the engine and check for oil leaks.
  14.  

3.8L Engine
  1. Disconnect the negative battery cable.
  2.  
  3. Remove the engine from the vehicle, as outlined earlier, then secure it to a suitable workstand.
  4.  
  5. Remove the flywheel-to-crankshaft bolts and the flywheel.
  6.  
  7. Unfasten the timing chain cover-to-engine bolts, then remove the cover.
  8.  
  9. Remove the camshaft sprocket-to-camshaft gear bolts, the sprocket, the timing chain and the gear.
  10.  
  11. To remove the balance shaft, perform the following:
    1. Remove the balance shaft gear-to-shaft bolt and the gear.
    2.  
    3. Remove the balance shaft retainer-to-engine bolts and the retainer.
    4.  
    5. Using the slide hammer tool, pull the balance shaft from the front of the engine.
    6.  

  12.  
  13. If replacing the rear balance shaft bearing, perform the following procedures:
    1. Drive the rear plug from the engine.
    2.  
    3. Using the camshaft remover/installer tool, press the rear bearing from the rear of the engine.
    4.  
    5. Dip the new bearing in clean engine oil.
    6.  
    7. Using the balance shaft rear bearing installer tool, press the new rear bearing into the rear of the engine.
    8.  
    9. Install the rear cup plug.
    10.  

  14.  

To install:
  1. Using the balance shaft installer tool, screw it into the balance shaft and install the shaft into the engine; remove the installer tool.
  2.  
  3. Clean the gasket mounting surfaces. Inspect the parts for wear and/or damage; replace the parts, if necessary.
  4.  
  5. Install the balance shaft retainer. Tighten the balance shaft retainer-to-engine bolts to 27 ft. lbs. (37 Nm).
  6.  
  7. Align the balance shaft gear with the camshaft gear timing marks. Install the balance shaft gear onto the balance shaft. Tighten the balance gear-to-balance shaft bolt to 15 ft. lbs (20 Nm), then using a torque angle meter tool, rotate another 35º.
  8.  
  9. Align the marks on the balance shaft gear and the camshaft gear by turning the balance shaft.
  10.  
  11. Turn the crankshaft so the No. 1 piston is at TDC.
  12.  
  13. Install the timing chain and sprocket.
  14.  
  15. Replace the balance shaft front bearing retainer and bolts. Tighten the bolts to 26 ft. lbs. (35 Nm).
  16.  
  17. Install the front timing cover and the lifter guide retainer.
  18.  
  19. Install the intake manifold and flywheel assembly. Tighten the flywheel bolts to 89 inch lbs. (10 Nm), plus an additional 90ºturn.
  20.  
  21. Install the engine assembly and connect the negative battery cable. Start the engine and check for leaks.
  22.  

 
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