I was using the gear rpm calculator and I don't know which transmission type to put in.. I put T-45 but I'm not sure.. I have a 96 AOD. If you know which Transmission type this is please let me know as I'm trying to figure out what my rpms will be at 75mph with 4.10 gears. Thanx in advance.
I don't know if the calculator will work for an automatic. Your transmission is a 4R70W. FWIW, I have 3.73s and the engine turns about 2600 rpm at 75 mph. With 4.10s, your engine should be 4.1 / 3.73 x 2600 = 2858 ==> 2900 rpm.
*edit*> Get a SpeedCal to correct your speedo/odo when you change the gears. It WILL work with your '96 auto (it does in my '98!). You can check your true speed by using the mile markers along the interstate and a stopwatch or you can use a GPS device (if you have access to one). Adjusting the SpeedCal is very easy. <*end of edit*