[patrickt]

Listen to olddog and run your exact speeds with the TKO600 gears, your rear, your tire sizes, and how those speeds correspond to the RPMs of your engine. For me, and my 15" wheels, 3.54 rear, and my .64 OD, it's absolutely perfect. My engine runs at its "quietest spot" at 2200 RPM, which corresponds to 75 MPH for me. One of my favorite things to do is head out on one of our lightly travelled interstates and just "quietly cruise" at 75MPH, which will not get you pulled over either. That is the only thing I ever use the OD for.