I found the 3.89 diff was near perfect for Sandown with my astron only needing 2 gears for the track once moving 3rd gear from turn 1 till the kink going up the back straight them 4th till dandenong corner back to 3rd till about the start finish lineSideways wrote:Yes, 3.9's are good for road cars but 4.6 to 4.8's are perfect for rally cars - top-end speed isn't so much of a priority - it's more about punch between corners
just run the engine up and down the rev range from 2500 to 7200
not sure how the 3.89 would work on the road at road speeds in 5th though , prob foul plugs it didn't like running that low in the rav range with out load for to long