Balance Shaft: Service and Repair

BALANCE SHAFT ASSEMBLY

Tool Required:

J 41088 Balance Shaft holding Plate


Remove or Disconnect


1. Negafive battery cable.
2. Engine oil pan, please refer to Engine, Cooling and Exhaust/Engine/Engine Lubrication/Oil Pan,Engine/Service and Repair/ Service and Repair






3. Balance shaft chaln cover.






4. Loosen but do not remove balance shaft chain tensioner.






5. Remove oil pump cover, then oil pump assembly.
6. Rotate engine crankshaft until number 1 piston is at TDC.






7. Use tool J 41088 to prevent the balance shafts from turning while loosening bolt.

NOTICE: The balance shaft driven sprocket bolt is left hand threaded and must be loosened by rotating it in a clockwise direction. If the bolt is not loosened in a clockwise direction, it may break.






8. Balance shaft driven sprocket bolt.

Important: Mark the surface of the driven sprocket if it is going to be reused. This will insure that the chain continues to ride on the same tooth surface. If a new driven sprocket will be installed, either surface can be placed against the shaft.

9. Driven sprocket from shaft.






10. Balance shaft assembly fasteners and remove assembly to bench (5 bolts).

Measure






Check balance shaft end play prior to disassembling the balance shaft housing.

a. Set up indicator to read off the back of the shafts.
b. Press against the one shaft and note movement.
c. Repeat step b on the other shaft.
d. Compare against specifications.
e. If out of specs, check if thrust plate for wear. Replace the thrust plate if it is worn. If the end play is out of specs and the thrust plate is not worn, replace the balance shafts.


Install or Connect

1. Install balance shaft assembly to engine block. Use GM P/N 12345493 on the housing to block bolts.










Tighten

Torque balance shaft assembly to engine block bolts to specifications.

2. Install balance shaft driven sprocket.


Tighten:

Torque balance shaft driven sprocket bolt (LEFT HAND THREAD) to 30 Nm (22 Lb. Ft.) + 45°. Use J 41088 to hold balance shafts in correct timed location.

3. Install engine oil pump, Please refer to Engine, Cooling and Exhaust/Engine/Engine Lubrication/Oil Pump, Engine/Service and Repair/ Service and Repair






4. Install balance shaft chain tensioner and torque to specifications.
5. Install balance shaft chain cover.
6. Install engine oil pan and gasket, please refer to Engine, Cooling and Exhaust/Engine/Engine Lubrication/Oil Pan,Engine/Service and Repair/ Service and Repair
7. Negative battery cable.