I'm using 3.25 gears, 29.1" tires and am turning 23-2400 rpm at 65 mph with a 1:1 ratio C-4 transmission. If I decide that I want to put the 3.79 gears back in, that same rpm will be about 55 miles per hour or about 10 mph less for the same wear and tear. It all has to do with economics - that is, your wallet, gas mileage and what your earlier engine wear will cost.