Hi and welcome to Answerpool
As I live in the Uk I'm more used to seeing Manual gearbox transmissions
But I'll have a guess if that's Ok? And say the reason for the failures could be that the Tab washers on the flywheel are either missing or not secure (bent up against the flywheel bolt faces)
or they have been bent up without torquing the bolts evenly (the flywheel is balanced)
And using old tab washers is not good practice (especially on a high performance engine)
There might be a Large thrust shim/Washer fitted behind the flywheel to dampen "end float" this means that the crankshaft will move laterally when it revolves, only a millimeter or so and this lessens that movement
Need a Haynes Manual exploded diagram of the engine or what ever to see if these are fitted?
The end result is a vibrating Flywheel which I hope has not damaged the splines on the crankshaft
Ps Check and replace the locating dowels if they can be removed (on the crankshaft end face) if these are bent too if they are the long type? Then the Vibes could continue?
Going to cost you a bit of time and Money on this...Sorry to be the bearer of Bad News
Post again and say what you found? Thanks
