I am interested to compare the affect of tires used today-and pressure used, wheel, and differential ratio to: actual rpm at 4th gear speeds of 50, 60, 70 mph. And compare to the old road tests and factory spec info…SO…on a drive…if you could have your passenger note the rpm at each speed in 4th (not Ovr-drive) , (it may be of interest to you to compare a gps speed to your speedometer.). Let me know the rpm at each speed…and also what tire your are running, your air press, and your diff axle ratio. I will make a chart…and share it.
For Example: 50 mph 2350rpm: 60 mph 2800rpm; 70mph 3210rpm with 3.77diff, Michelin Pilote X @32psi on 5inch wide wire wheel. (or a 5.5inch disc, or a 6 inch wide wire)