I might be way off base here, but from reading in different forums, I've put 2 + 2 together and think that there's a problem.
From what I've read, it is highly suggested that the driveshaft be replaced if either the gear ratio or the rev limit is raised. It has been mentioned that our driveshaft itself is the reason that the MM top speed is as limited as it is. With 4:11's or higher, I've read that we shouldn't exceed 90 MPH. Could the stock driveshaft be responsible for pinion seal failures? I'm at 22,000 miles. I don't drive fast (often), but I rev this beast to red line every single day. These cars are not doing 6,000 RPM's at 115 miles per hour, but that's where mine shifts at when WOT. My driveshaft sees these kinds of engine RPM's a dozen times each day.
Any input on this?