Input Shaft Spigot Bearing Woes

[wherzmespana]

I have now had 3 failures of the spigot bearing that sits in the end of the crankshaft to receive the input shaft spigot. I am running an LS1 with a G50 gearbox. The car is 99% track use so spends next to no time sitting in neutral or slipping the clutch but the bearing only seems to last for 500 miles or so? Help.....................

[GTWayne]

Sounds like the input shaft is not running true.

[CanAm Dave]

Hi Mike

Did you dial in the adapter plate. Most people just fit them without much thought but its worth taking the time and checking it. The alignment of the plate is critical to the true running of the input shaft in the spigot bearing. You can use offset dowels in the block to adjust the alignment of the plate.

Regards Dave

[Steve_D]

Whose adaptor plate do you have?
If this is poorly made then the shaft could be out of line putting a side load on the bearing.

Has the clutch been replaced at any time before or during these failures?
Just thinking that if the clutch were out of balance then this may cause the problem but I'm less convinced.

What is the mode of the bearing failure? A description or pic of the failed bearing may help.

Steve

[Boosted LS1]

Tell me more Mike. When you say failures, what do you mean? Something getting hot, something falling apart, something noisey, dry bearing? Is there slop between the bearing and input shaft? 3 failures indicates a common problem but that should make diagnosis easier.

The above comments are valid but machining the adaptor on the piss is really poor, could happen though, rarely. Make an insert to fit the rear of the crank and use that as a datum to check runout of the adaptor. Mike.


ETA, are you using quality bearings?

Edited by Boosted LS1 on Monday 28th July 23:34

[andygtt]

yeh sounds like either an input shaft problem (maybe bent or modified in some way) or the adapter is out.... that bearing should not fail in your car.