Originally Posted by Transman
Overdrive transmissions have no impact on the prop shaft speed.





In a way they do... most production driveshafts are generally balanced for 3000-3500 rpm, when you add an overdrive transmission along with let's say a 4:10 rear gear, .... a .64 overdrive is now capable of moving the vehicle to a speed of 140-150 mph with engine rpm being the limiting factor, prop speed is now extremely high, one of the reasons most aftermarket overdrive suppliers balance the shaft to 10,000 rpm