Improper Pilot Bushing Installation

[jss06c6]

Bill Boudreau and I discussed before and after tear down. Grease contaminated the oilite bronze bushing (not a bearing), destroyed the lubricating properties of the oilite bronze. Input shaft tip galled as a result. Bushing was set shallow. When the trans was bolted up, the input shaft face was pressed against the bushing face, causing more heating from friction caused by loss of lubricating properties of the oilite bronze. Add to this a flywheel that was not planar causing erratic engagement with the clutch and pressure plate and you've got a recipe for disaster.

Clutch, flywheel and pilot bushing were NOT installed correctly.

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[Top Toy]

It appears from the photos that the failed bushing was a plain bore as opposed to the fluted style generally recommended today. The flutes provide a place for any contaminants to accumulate without compromising the already tight clearance between the OD of the pilot shaft and the ID of the bushing. If, in this case, the shoulder of the pilot shaft was riding hard on the face of the bushing, that would have caused the tip of the shaft to heat up when it was stationary and the flywheel was spinning (clutch depressed in gear) and expand to the point where there was an interference fit between the shaft and bushing. Having grease in that tight gap would only have made matters worse since it had no place to go and likely started coking in the heat. The metal particles in the mix probably came from the shaft itself as it heated up and flaked off.

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[jss06c6]

Originally Posted by Top Toy

It appears from the photos that the failed bushing was a plain bore as opposed to the fluted style generally recommended today. The flutes provide a place for any contaminants to accumulate without compromising the already tight clearance between the OD of the pilot shaft and the ID of the bushing. If, in this case, the shoulder of the pilot shaft was riding hard on the face of the bushing, that would have caused the tip of the shaft to heat up when it was stationary and the flywheel was spinning (clutch depressed in gear) and expand to the point where there was an interference fit between the shaft and bushing. Having grease in that tight gap would only have made matters worse since it had no place to go and likely started coking in the heat. The metal particles in the mix probably came from the shaft itself as it heated up and flaked off.

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Spot on ...

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[WARP TEN]

Originally Posted by Paul Workman

Interesting topic, 'fer sher'.

That said, and having serviced many a clutch, starting with my part-time job as a mechanic, back in my college dayz, I became slightly paranoid about riding the clutch; either at a stop light or waiting for an opening in bizzy city traffic.

Agree--I long long ago developed the habit of always putting the car in neutral and getting off the clutch when at a stop. Always did it. Never had a clutch or bushing failure even when the clutch had been in for 75,000 miles or more.--Bob