If you are cruising at high RPM, you don't have a 3.08 rear. You should not be turning more than 2300 RPM at 70 MPH with a 3.08 gear If you have a Tach, then set 60 mph, and record your RPM and then go into the calculator Willys steered you to and compute your rear end ratio (RER). No tach? Then remove your cover or slide out your 3rd member and count the teeth on the ring gear (big gear) and Pinion (small gear) and divide the little number into the big number and the result is your gear ratio. I have never had good luck turning the rear wheels and counting drive shaft turns. Come up with a different answer each time I try it!!!