I am always interested in finding out about different parts and setups and techniques for my car, that will benefit on the track as well as on the street. But I want to consider downsides as well as benefits. It's rarely as simple as some people make it out to be.

I have not installed a shorter final drive in my ITR. Aside from the cost - certainly a significant downside - the fact that the stock FD accelerates substantially (~18 percent) faster than the shorter one at speeds of 79-88 mph, where a lot of driving takes place at the tracks that I frequent. It's faster because I can stay in third gear rather than being forced to upshift to fourth and be slower with the shorter FD. This makes me believe that the shorter FD will overall be no faster, and may in fact be slower, than the stock one.

Some people perceive that the shorter FD is faster, because it reaches redline faster. But most of reaching redline faster is because that occurs at a lower road speed, rather than actual acceleration benefits. So it seems like it improves acceleration in any given gear much more than it actually does - and that is before taking into account the poorer acceleration it provides when it is forced to upshift to a higher gear at a lower road speed than the stock FD.

If I were more interested in drag strip performance than in road courses, I would probably get the shorter FD, because its acceleration benefits are more consistent at lower speeds. But acceleration below 50 mph is of little importance to me.


What that will do is shift those "speed bands", just like a shorter one does. I like the stock FD because of its ability to keep me at the top of third gear at the speeds noted above. The stock FD will be quicker at 79-88 mph, where it is at the top of third gear, than the taller FD or the shorter one.