Missing a downshift,what did i damage?

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Originally Posted by milliemax

John99boxter and I were just talking about this 2 days ago and we think this is where most IMS failures come from. This is a good subject that is not talked about. "Secret Abuse" "Missed Gears" ???? Lets take a good look at our selves, not just the bearing.

I think this is unlikely. Bearings like the IMS can often withstand very high rpm, some as high a 100k rpm. When an engine fails from temporary over-rev, it is usually either valve float causing piston/valve contact or rotating mass imbalance resulting in rod bolt failure or loads exceeding oil float. I'm sure Jake or JFP have a lot more direct experience in seeing the failure modes and causes, but most over-rev killed motors I have seen are characterized by valve knock or connecting rods sticking out of the case. The IMS bearing was still sound.

From the examples so far, I think IMS bearing failure is more likely moisture contamination causing pitting of the rolling surfaces and high load/low rpm such as lugging the motor off the line or in stop and go traffic. Cars that sit idle for many months do seem to have a higher failure rate than car with a lot of track miles.

No hard data so this is all a thought experiment based on anecdotal evidence.