Walter White, Jake is spot on with the comment that spinning an unloaded bearing does not reflect what is happening in the engine. Ivory tower bearing life (all other things being equal) is related to load and RPM. The implication is that operating temperature lubrication, vibration, contamination are all nominal for the bearing. Take a look at bearing manufacturers design handbooks for more information. The reason I did not perform an L-10 calc for the IMSB was because the load would have to be an estimate making the result worthless. By the way, RPM is at 1/3 crank speed. As far as changing the IMSB, Porsche should have manned up early and declared it a maintenance item, particularly the single row
. As has been pointed out below, every part of a car eventually fails, the trick is to understand required maintenance to head off collateral damage from failed parts. To reduce the chance of IMSB failure in my engine, the intermediate shaft was modified and the bearing replaced with a high temperature C3 single row bearing. The bearing will be changed out as if it were a timing belt. That means scheduled bearing replacement, something Porsche dealers should have been doing years ago.
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