GM Astro/Safari 1985-1996 Repair Guide

Balance Shaft

Print

The higher performance VIN W engine was given a balance shaft (in addition to the usual crankshaft damper) in order to help smooth the engine. It is gear driven directly from a sprocket mounted between the camshaft timing sprocket and the camshaft itself.

REMOVAL & INSTALLATION



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



Click image to see an enlarged view

Fig. Fig. 1: Balance shaft drive (lower) and driven (upper) gears



Click image to see an enlarged view

Fig. Fig. 2: Exploded view of the balance shaft mounting-VIN W engine



Click image to see an enlarged view

Fig. Fig. 3: Remove the balance shaft using a soft-faced mallet



Click image to see an enlarged view

Fig. Fig. 4: GM shaft service kit, set-up to remove the shaft rear bearing



Click image to see an enlarged view

Fig. Fig. 5: Removing the shaft rear bearing using the service kit



Click image to see an enlarged view

Fig. Fig. 6: Installing the balance shaft rear bearing



Click image to see an enlarged view

Fig. Fig. 7: Using the shaft installer and driver handle to drive the shaft into position



Click image to see an enlarged view

Fig. Fig. 8: Balance shaft drive and driven gear timing mark alignment

  1. If equipped, properly discharge and recover the A/C refrigerant, using a suitable recovery station. If you do not have certification for and access to such equipment, take the vehicle to a reputable repair facility and have the system discharged.
  2.  
  3. From inside the vehicle, remove the engine cover. For details, please refer to General Information & Maintenance of this information.
  4.  
  5. Properly relieve the fuel system pressure, then disconnect the negative battery cable.
  6.  
  7. Place a catch pan under the radiator, open the drain cock and drain the cooling system.
  8.  


CAUTION
When draining the coolant, keep in mind that cats and dogs are attracted by ethylene glycol antifreeze, and are quite likely to drink any that is left in an uncovered container or in puddles on the ground. This will prove fatal in sufficient quantity. Always drain the coolant into a sealable container. Coolant should be reused unless it is contaminated or several years old.

  1. Remove the air cleaner box and air intake duct.
  2.  
  3. For 1996 vehicles, remove the A/C compressor, bracket and accessory drive bracket (as equipped). Immediately plug all openings in the A/C system to prevent system contamination.
  4.  
  5. Remove the engine cooling fan.
  6.  
  7. Remove the radiator assembly.
  8.  
  9. On 1992-94 vehicles, remove the headlight bezels.
  10.  
  11. Remove the grille.
  12.  
  13. Remove the air conditioner condenser. Immediately plug all openings in the A/C system to prevent system contamination.
  14.  
  15. Remove the water pump assembly.
  16.  
  17. Remove the crankshaft pulley and torsional damper.
  18.  
  19. Raise and support the front of the vehicle safely using jackstands.
  20.  
  21. Remove the oil pan.
  22.  
  23. Remove the front timing cover.
  24.  
  25. Remove the camshaft sprocket, timing chain and balance shaft drive gear.
  26.  
  27. Remove the balance shaft driven gear.
  28.  

The balance shaft drive and driven gears are to be serviced ONLY as a matched set. This set INCLUDES the balance shaft driven gear bolt.

  1. Remove the balance shaft retainer.
  2.  
  3. Remove the intake manifold assembly.
  4.  
  5. Remove the hydraulic valve lifter retainer.
  6.  
  7. Remove the balance shaft from the bearing using a soft faced mallet.
  8.  
  9. Remove the rear bearing using tool J-38834 and J-26941 or equivalent balance shaft bearing service kit and needle bearing removal tool.
  10.  

The balance shaft and front bearing are to be serviced or replaced only as a complete assembly. DO NOT attempt to remove the front bearing from the shaft.

To install:
  1. Dip the bearings in clean engine oil before installation.
  2.  
  3. Using tool J-38834, install the balance shaft rear bearing with the flat edge and the manufacturer's markings facing the front of engine.
  4.  
  5. Dip the front balance shaft bearing into engine oil. Using tool J-36996 and J-8092 or equivalent shaft installer and driver handle, install the balance shaft into the block.
  6.  
  7. Install the balance shaft retainer and torque the bolts to 120 inch lbs. (14 Nm).
  8.  
  9. Install the balance shaft driven gear. Install the bolt and torque to 15 ft. lbs. (20 Nm) plus turn the bolt an additional 35 degrees (using a torque angle meter).
  10.  
  11. Install the lifter retainer and turn the balance shaft to ensure proper clearance. If clearance does not exist, the lifter retainer may have to be replaced.
  12.  
  13. Turn the camshaft so that the timing mark on the balance shaft drive gear (temporarily installed) is facing straight upward (toward the driven gear).
  14.  
  15. Remove the drive gear, then turn the balance shaft so that the driven gear timing mark is facing straight down (toward the camshaft and drive gear (when it is reinstalled).
  16.  
  17. Install the drive gear to the camshaft, making sure that the timing marks on the drive and driven gears are still in alignment (dot-to-dot).
  18.  
  19. Install the balance shaft drive gear retaining stud and torque to 12 ft. lbs. (16 Nm).
  20.  
  21. Install the intake manifold assembly.
  22.  
  23. Align and install the timing chain and camshaft sprocket.
  24.  
  25. Install the front timing cover.
  26.  
  27. Install the oil pan.
  28.  
  29. Install the crankshaft pulley and torsional damper.
  30.  
  31. Install the water pump assembly.
  32.  
  33. If equipped, install the air conditioner condenser.
  34.  
  35. Install the grille.
  36.  
  37. On 1992-94 vehicles, install the headlight bezels.
  38.  
  39. Install the radiator assembly.
  40.  
  41. Install the engine cooling fan.
  42.  
  43. On 1996 vehicles, install the A/C compressor, bracket and accessory drive bracket (as applicable).
  44.  
  45. Install the air cleaner box and air intake duct.
  46.  
  47. If not done already, remove the jackstands and carefully lower the vehicle.
  48.  
  49. Refill the engine crankcase using fresh engine oil, then connect the negative battery cable.
  50.  
  51. Properly refill the engine cooling system, then check for leaks.
  52.  
  53. Once the engine has cooled sufficiently, install the engine cover to the passenger compartment.
  54.  
  55. If the A/C system was discharged, take the van to a reputable repair facility to have the system evacuated, recharged and leak tested. DO NOT WAIT LONG to do this or moisture which entered the system while it was discharged will cause corrosion and internal system damage. ALSO, DO NOT run the compressor until the system has been properly recharged. Depending on how your model is equipped this may mean you CANNOT use the defogger (this automatically turns the compressor on in some vehicles).
  56.  

 
label.common.footer.alt.autozoneLogo