Thanks guys. So if the stock rear gear, at the lowest is 3.90, I should "theoretically" have a decent cruising rpm with overdrive?

This is the equation im using to determine cruising RPM. MPH x Gear Ratio x OD x 336/Tire Diameter So....75MPH x 3.90 x .68 x 336 / 29 = 2304 RPM (3.73 gear was a little better obviously, but im not gonna be that picky) Of cousre, I havent taken into consideration vehicle weight so thats may be variable to take into account.

Bartamos I found an '87 rear diff with 3.73, did you have to move leaf spring saddle to fit on yours?



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