M12 T56 issues

[WS6]

I do not know the internal workings on a manual transmission, especially the T56. So I need insight from those that do. I have a customer with a C5 Z06 with stage 2 procharger and 3.90 gears. The car makes 540rwhp and 450 ftlbs. He lives around two hours out so I have not seen the car yet. I am going on what he is describing.



The car starts to make a howling noise as you approach 60. It gets very loud around 70. This is in 6th gear. If you press the clutch in, the noise stops instantly. The noise does not occur while accellerating up to 60 and 70 mph through the other gears. It does not seem to be related to rpm at all actually.

Any ideas on what it could be? I have him trying some different things like pressing the clutch in around 70mph and then putting the car into neutral and coasting. Also putting the car in 4th and 5th while the noise is occuring to see if it goes away. What else should he try so we can start to eliminate the possibilities. My limited knowledge points me towards something wrong with 6th gear or input shaft issues.

The car is not drag raced or beat on excessively. He drives it like a hot rod. He uses the power from time to time but I wouldn't call it abusive. Rides on Kuhmo MXs

Thanks