Removal & Installation
Any time one shaft needs to be replaced, both shafts must be replaced. Anytime the shafts are replaced, the bearings much be replaced.
The transaxle assembly must be removed from the vehicle to perform this procedure.
- Disconnect the negative battery cable. Remove the transaxle.
- Matchmark and remove the pressure plate and clutch. Remove the flywheel mounting bolts, the flywheel retainer on automatics and the flywheel.
- Remove the engine oil pan. Remove the nut/bolt securing the balancer shaft chain cover and cover.
Loosen the pivot bolt on the chain tensioner and pivot the tensioner to remove the tension from the chain.
CAUTIONThe balance shaft sprocket bolt is reverse threaded and must be rotated clockwise to be removed. Turning the bolt in the counterclockwise direction can result in the bolt shearing off in the balancer shaft.
- Hold the crankshaft from turning and remove the balancer shaft sprocket bolt.
- Mark the balancer shaft sprocket so the same side of the sprocket is facing the engine during installation.
- Separate the sprocket from the balancer shaft.
- Remove the 5 balance shaft assembly-to-engine block mounting bolts. DO NOT remove the 8 bolts holding the balance shaft housing halves together.
Pry the oil pump pickup screen out of the housing.
- Support the balancer shaft housing and loosen the 8 mounting bolts in the reverse order of the tightening sequence.
- Remove the 8 bolts and lift the top half of the balance shaft housing off. Remove the 2 balance shafts from the housing.
- Remove the balance shaft bearings. Remove the thrust plate bolts and plate.
Inspect the shafts for scores or burrs on the journals. Inspect the gears for missing or chipped teeth.
NOTEDo not attempt to resurface the balance shaft journals. They may have a slight taper and resurfacing the journal may remove the taper.
Insect the gears for backlash:
- Place the gear and shaft assemblies in the housing. The bearings must be installed.
- Ensure the timing marks are lined up.
- Set up a dial indicator to read off one of the tooth of the balance shaft gear.
- Hold the other shaft.
While pulling both shafts in the same direction, gently rock the gear in the direction of rotation to ensure proper measurements.
NOTEIf the shafts are not pulled at the same direction, the gears will climb away from each other causing the reading to be incorrect. Do not rotate the gear as you will get incorrect readings.
- Note the total movement and compare specifications.
If the backlash is out of specifications, replace both gear and shaft assemblies.
- Clean all the components thoroughly. Install the thrust plate and tighten bolts to 115 inch lbs. (13 Nm).
- Carefully install the new bearing inserts into the housing halves. Use care not to scratch or gouge the bearings or the housing.
- Lubricate the bearings, balance shaft and gears with GM 9985705, or the equivalent.
- Install the balance shafts into the lower half of the housing. Make sure the timing marks on the balance shafts are lined up properly.
- Install the upper half of the balance shaft housing and tighten the bolts in sequence to 44 inch lbs. (5 Nm). DO NOT tighten the bolts any tighter at this time. The final housing bolt tightening is done after the assembly is installed on the engine.
- Do not install the oil pump pickup screen until the bolts have been tightened to their final torque.
- Install the balance shaft assembly on the engine and after coating the mounting bolt threads with Loctite® 242 or equivalent threadlocking compound tighten the bolts in sequence to 44 inch lbs. (5 Nm).
Tighten the 5 housing-to-engine bolts as follows:
- Bolt 1 to 18 ft. lbs. (25 Nm).
- Bolt 2 to 18 ft. lbs. (25 Nm).
- Bolt 3 to 30 ft. lbs. (40 Nm).
- Bolt 4 to 18 ft. lbs. (25 Nm).
- Bolt 5 to 39 ft. lbs. (53 Nm).
- Tighten bolt 1 an additional 70 degrees.
- Tighten bolt 2 an additional 70 degrees.
- Tighten bolt 3 an additional 60 degrees.
- Tighten bolt 4 an additional 70 degrees.
Tighten the 8 upper-to-lower housing bolts, in sequence, to:
- Bolts 1 and 2 to 89 inch lbs. (10 Nm).
- Bolts 3 to 11 ft. lbs. (15 Nm).
- Bolts 4 through 7 to 89 inch lbs. (10 Nm).
- Bolts 8 to 11 ft. lbs. (15 Nm).
- Tighten all 8 bolts in sequence an additional 40 degrees.
- Rotate the balance shaft assembly 1 full revolution to verify the shafts spin freely. Make sure the balance shaft assembly is returned to its original position before installation of the drive sprocket and chain.
- Rotate the engine until the No. 1 cylinder is at Top Dead Center. Rotate the engine 90 degrees.
Install retaining tool J 41088 onto the balance shaft assembly to ensure the balance shafts don't rotate when the driven gear is installed.
- Install the balance shaft driven gear with the mark made during disassembly facing outward and tighten the left hand threaded mounting bolt to 22 ft. lbs. (30 Nm).
- Remove retaining tool J 41088.
Install the balance shaft chain guide and set the chain tension as follows:
Insert a 0.040 inch (1mm) brass feeler gage between the chain guide and the chain.
NOTEA brass gage must be used to ensure proper chain tension. Use of a steel gage will not provide the correct flex and the chain tension will be incorrect.
- Press the chain guide against the chain with 3 lbs. of force.
- Tighten the chain tensioner adjuster bolt to 115 inch lbs. (13 Nm).
- Install the balance shaft chain cover and tighten the nut/bolt to 115 inch lbs. (13 Nm).
- Insert a 0.040 inch (1mm) brass feeler gage between the chain guide and the chain.
- Install the oil pan assembly. Install the flywheel and tighten bolts to 22 ft. lbs. (30 Nm) plus 40 degrees additional rotation.
- Install the clutch disc and pressure plate. Install the transaxle assembly.
- Connect the negative battery cable. Start the vehicle and verify the engine runs smoothly and quietly.