Your actual speed will be 1.5% faster than what the speedometer reads.

4.08 gears = ~10% more aggressive than 3.7 gears, but not necessarily 10% faster acceleration.

Stop speculating and just get the gears installed. ;)

I bought the 4.08 gears but the don't fit the diff hemisphere. Anyone know why

I swapped my gears for 4.08 when I changed my LSD and have no regrets . Car launches way better and goes through gears like lightning . In for 4 years with zero problems to date .

Also, not sure why everyone says first gear is useless ??? U burn through it a lot quicker but my oh my it's fun ..

I'm guessing the 4.08 makes the gears longer. There's no way anyone uses 1st gear at wot. Too short on stock gears, almost no traction at wot.

Is anyone using the 4.08 0r 3.09 gear with a supercharged ride.
I am looking at this mod and would like some advise - to do or not to do , 4.08 or 3.90 with supercharger

Is this mod affecting idle rpm's?

has anyone found a solution to "losing" revmatch when going with 4.08? since the 15 nismo has 3.98 or whatever, does this mean nissan has the ability to "tune" the revmatch system? wonder if they would be willing to do that for you.

no, its the final drive ratio. Only effects the mechanical advantage of power through the driveline when the car is in gear. engine/flywheel/clutch or torque converter if your auto/transmission/drive shaft, rear diff "where FD is located"

The final drive determines the ratio of how many revolutions the driveshaft makes to turn the rear differential or tires one turn, or 1 foot radius to be more precise. if its a 4.08 to 1 the drive gear rotates 4.08 times and the driven gear rotates once.

Rev match will not be lost. I believe it is based on engine RPM, trans input & output speeds.

i didnt really mean "lost" per say. More like its not accurate anymore. Or so ive heard from everyone who changed their FD.

I personally think the FD swap needs to be done depending on what your requirement is, on which track/road course or whatever..

while the shorter FD increases 1st gear launching and give you out of the hole G force, you need to remember that you will have to shift earlier, and depending on what kind of power band you will be sitting in which gear, the FD might actually make your car run slower because you will be out of your power band earlier, just as you would be in the band earlier. Depending on which gear you will be in most of the time, this may help or hurt your results. But shorter FD generally makes the driver a bit more busy/alert which is always fun :D and I think that helps with lap time.

Back in my 350Z days started almost 10 years ago, people were craving about 3.9 FD set (stock is 3.5 in 350Z) and I got that swapped out when I was doing the LSD. The track I went to quite regularly was pretty much spot on for the 3.9 because I could run in 3rd gear all the way in the areas where I had to use 2nd and 3rd gear. But in some other cases, I had to shift a lot more and it seemed to eat up my time. With shorter FD It seemed more frequent to fall in to the band where it was awkward to either stay in gear or shift up.

You need to remember, while a car with shorter FD will accel faster when compared to a stock geared car gear to gear, 3rd gear to 3rd gear for example, shorter car's 3rd gear will be accelerating slower than stock cars 2nd gear and if you happen to shift into 3rd where stock cars can stay in 2nd - you are losing.

Not sure how 4.1 would feel.. probably a bit too short? I found 3.9 somewhat short already, but that's compared to 350Z's stock 3.5 FD. However the extra HP of 370Z probably will make it feel a lot shorter.

Funny how we cant really settle with the stock settings and always try to make it slightly different in the hopes of improvement. Even if the cars came with 3.9FD people would still try the shorter gear :D

I gotta try the same track with my 370Z, only recently got the car and haven't had a chance to visit a track yet. :eekdance:

Hey man quick question does your SRM and cruise control still work with the 4.08 FD?

Don't think you're going to get most of those posters to answer given how long ago this thread is from.

To answer your question, the SRM requires a re-calibration via ECUTEK or Uprev to consistently work with a 4.08 FD set.

Didn’t realize this thread went over 3yrs without a comment...I know if you’re running stock diameter tire’s-your speedometer won’t be affected,as wheel speed sensors are on the output shafts of pumpkin cover-reading speed of stub shafts/ from the toner rings.