A T5 works best with a 3.73 rear axle IMO. The 3.42 and 3.90 gears are also good.
For a good driver, car or truck, use this rule of thumb as a guide.
First gear X rear axle should give a number between 9 and 12, and the OD gear X the rear axle should be between 2.8 and 3.
Example: A 1965 factory C10 three speed tranny had a 2.94 first gear and 3.73 was common for the rear axle. (2.94 X 3.73 = 10.96) As a work truck it could haul stuff with that 10.96 number. A lighter vehicle does fine with a number closer to 9.
An OD gear X rear axle should be a number between 2.8 and 3.0. If the vehicle is very heavy, or doesn’t make much horsepower in the 1800 to 2000 RPM range, then it’s more desirable if the number is closer to 3 than 2.8. A SBC with good HP can handle 2.8 and sometimes lower.
Example: My 1963 230ci doesn’t make much HP even though it runs great. Good compression too. A 230 just doesn’t make much HP.
I have a 0.76 OD in the T5 and a 3.73 rear. It does fine on the highway without lugging. So 0.76 X 3.73 = 2.83
Last edited by Lugnutz; 11/01/2021 10:19 PM.
