So I'm considering going with a supercharger in the next year or two on my 5AT, but I'm already not a fan of 3k rpm @ 80mph, especially if I'm going to be pushing more power (I've also heard horror stories about 1st gear being useless after a certain power point). Has anybody reduced their final drive after going FI? I only know about people increasing their final drive on NA 5AT, but I've never heard about people reducing it, or even know where to get a lower final drive that bolts up to the rear axle. A final drive ratio that reduces 80mph rpm to 2.6k-2.8k instead of 3k sounds like a nice combo with some FI adding power to make up for the reduction.

Is this even possible?

 

Anything is possible. Do you know your diff's stock ratio? You can go from there.

 

It depends on what you're building the car for.

 

What year is your car? 03-06 5AT already come with a pretty tall 3.3 final drive.

07-08 w/ 5AT have a shorter 3.69 FD, so you have the option of going to 3.54 or 3.3.

Available Nissan OEM final drive ring and pinion gear sets that will fit your case are: 3.3, 3.54, 3.69, 3.9, 4.08, and 4.36 ratios.

Honestly, your highway cruising rpm shouldn't really be your main concern. When people say first is useless, they're talking about a manual trans anyway, not an auto.
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