20.05.2012, 13:06
The knocking noise is being generated within the transmission (gear rattle) and is being caused by the dual-mass flywheel not being able to completely dampen the pulses of energy particularly at idle when they are at their greatest level. The occurrence of gear rattle is absolutely harmless to the transmission but can be audibly annoying. The noise is generated when gear contact switches back and forth from the drive surface to coast surface between the front drive and driven gears within the transmission. The click-clack effect (gear rattle) won’t harm anything so you can continue to operate vehicle while you sort out the cause.
The “at idle” gear rattle can be caused by a failing damper within the dual-mass flywheel (less likely) or can be caused by an ignition miss-fire (more likely) with the ignition system. It is possible for the ignition system to become slightly degraded to the point where only at idle is a problem detectable. Check the spark plugs, spark plug wires and coils per factory service manual procedures. Factory service manuals can be purchased on line through http://www.helminc.com .
The reason why the last pilot bushing failed is likely because someone made mistake of applying grease in the bushing causing it to fail within two or so years. Grease dries up and clogs the normally self oiling pours of the oil saturated bushing. Glaze then develops on the pilot tip and eventually the pilot bushing binds and spins in it’s journal. Be sure to replace pilot bushing with GM fluted pilot bushing (GM P/N 10125896) when possible. New fluted pilot bushing is to be installed clean, bright and dry. Grease is okay to put on pilot tip only when installing a pilot roller bearing. The thin grooves (flutes) in the fluted pilot bushing will act as scrubbers to prevent glaze build up on the input shaft pilot tip. There is plenty of oil stored in the bushing to lubricate the pilot tip for life-cycle of the clutch.
The input shaft main bearing is very stout. I have never seen or heard of one of these bearings ever to fail. Usually what starts out seeming to be a main bearing issue usually turns out to be a pilot failure. The rear wheels will tend to spin at idle with no gear engaged when up on lift. Applying e-brake will better simulate normal weight-on-wheels condition when up on lift.
Normal life expectancy of the dual-mass flywheel should be 2 or 3 clutch life-cycles. If dual-mass flywheel is found to have faulty damper (grease leaking from it), there are new replacement ZR-1 (eight bolt) dual-mass flywheels still available in Florida for around $750 plus shipping. The dual-mass flywheel assembly is comprised of 142 individual parts amazingly enough.
The “at idle” gear rattle can be caused by a failing damper within the dual-mass flywheel (less likely) or can be caused by an ignition miss-fire (more likely) with the ignition system. It is possible for the ignition system to become slightly degraded to the point where only at idle is a problem detectable. Check the spark plugs, spark plug wires and coils per factory service manual procedures. Factory service manuals can be purchased on line through http://www.helminc.com .
The reason why the last pilot bushing failed is likely because someone made mistake of applying grease in the bushing causing it to fail within two or so years. Grease dries up and clogs the normally self oiling pours of the oil saturated bushing. Glaze then develops on the pilot tip and eventually the pilot bushing binds and spins in it’s journal. Be sure to replace pilot bushing with GM fluted pilot bushing (GM P/N 10125896) when possible. New fluted pilot bushing is to be installed clean, bright and dry. Grease is okay to put on pilot tip only when installing a pilot roller bearing. The thin grooves (flutes) in the fluted pilot bushing will act as scrubbers to prevent glaze build up on the input shaft pilot tip. There is plenty of oil stored in the bushing to lubricate the pilot tip for life-cycle of the clutch.
The input shaft main bearing is very stout. I have never seen or heard of one of these bearings ever to fail. Usually what starts out seeming to be a main bearing issue usually turns out to be a pilot failure. The rear wheels will tend to spin at idle with no gear engaged when up on lift. Applying e-brake will better simulate normal weight-on-wheels condition when up on lift.
Normal life expectancy of the dual-mass flywheel should be 2 or 3 clutch life-cycles. If dual-mass flywheel is found to have faulty damper (grease leaking from it), there are new replacement ZR-1 (eight bolt) dual-mass flywheels still available in Florida for around $750 plus shipping. The dual-mass flywheel assembly is comprised of 142 individual parts amazingly enough.
Hier in Bavaria, wo die Bäume noch aus Holz sind!
Hier in Bavaria, wo die Schafe selten Brillen tragen!
Monthy Python
Hier in Bavaria, wo die Schafe selten Brillen tragen!
Monthy Python