My transmission is a 700r4 and i have 35" tires.
My car has an automatic transmission.
The required gear is determined by the number of speedometer drive gear teeth in the transmission output, the rear end gear ratio (3.89, 3.08, 4.11, etc.), the tire diameter, and the number of RPM’s the speedometer needs to "see" at a standard 60 MPH. If you input these data in a speedometer gear calculator the appropriate gear will be output. There are also tutorials at the 700R4 transmission page which explain each step of the process, that is how to select the right vehicle input data or parameters. If you are interested in a transmission replacement, YourMechanic professionals in certain locales can assist with that. Please simply inquire based on your locale. If you have further questions or concerns, do not hesitate to re-contact YourMechanic.