Hi there Mr. White,
Just wanted to jump in and offer a little information on this.
During the testing of the 3.90 gear changes Ricardo informed us that there might be a little gear noise on some cars. We asked why, and they explained that because of the cut of the gear, some cars might experience a little whine on decel. We ended up shipping all of our inventory back to Ricardo and asked that they re-cut the gears and ask that they surface them so there would be as little noise as possible. They went through and serviced every gear set and all efforts were made to minimize the possibility as much as possible.
In fact, the first two cars that we did the gears on were both done with the original gear sets and we offered to do a free replacement on those gears if the customer desired. One customer said he liked the whine and wanted to keep it and the other customer did return to our shop for the revised gearset. However, those were the only two gearsets ever installed in car's with the original cut. After those two all of our inventory was returned to Ricardo.
Now, with that being said, we have noticed a little bit of gear whine on some of the 3.90 cars as well as factory cars with unmodified gearsets. As stated by Ricardo on numerous occasions, it is normal and not something to be concerned about. Especially if the whine is on decel. If the whine was noticable under acceleration then we would be a little concerned. Remember, this transaxle is basically a racing transaxle. It will have little noises and odd characteristics that are normal for transaxles of this type.
It is my understanding that Shadowman has driven the car after the concern initially came up and after discussing everything with our tech's and the Ricardo engineer's the noise is not a concern in regards to any mechanical issue presenting itself.