Hey guys,

Just got an '07 ap2, and apparently it has a different final drive than stock (everything else should be stock). A noticeable improvement in low speed acceleration over my friend's stock s2000 triggered this observation. So, what is the easiest way to figure out the ratio of my final drive gear? I also do not have a speedometer re calibrating device on the car, or not that I know of.

 

In 6th gear at 75mph, the engine should be turning right at 4000rpms. Compare your car in the same gear and the same speed, do a little math, and you'll have your answer.

If your car is turning 5000 rpms, then the math would be (5000/4000)*4.1. This would give you the ratio of your final drive.

 

If you have a smart phone chances are it has a GPS that you can use to check your speed. There is also a free app you can get called Speedbox. This app is a GPS speedometer and will give you a display of how fast you are going for you to compaire with the cars spedo.

You can mark the input flange and one of the stub axles so that both marks line up, count the revaluations as you turn the input flange. For a stock 4.10 ratio the 2 marks will realign in 4 full turns plus a 10th past the mark. If a 4.44 it will take I bit less than 4 and a half turns to realign. This I hope gives you a basic idea on how to figure out what you have, good luck

 

Marking the axles and counting the driveshaft revolutions is the sure fire way to tell what your gear ratio is.

 

So could I go about it by putting the car on jack stands in a gear and turning a rear wheel 1 revolution and tracking how much the driveshaft spins?