http://performancenissanparts.com/ca...oducts_id=2087

Just wondering if anyone here has changed to the 3.917 Final Drive Gear. I think they say it's about a 10% reduction. I guess I'll have my G soon enough to find out myself, but I still wanted input from others on this: Is 6th tall enough (low revs at 70-80mph) that such a reduction wouldn't be that bad on the highway?

 

Great mod but it would mess with warranty.
Yes with an OEM of about 3.5/1 ratio on the 6M/T, the 3.9 would be about a 10% reduction, and a very easy way to gain quickness.
It would cost somewhat in comefort and mpg's at highway speed tho.
G/L with yours
C.

 

lower profile tires...i.e. smaller wheel+ tire diameter will have the same effect....try running 265/35 18's instead of the 245/45 18/s...the look better plus the car is quicker.....only problem is the speedo whether you change the tires or final gear ratio needs to be recalibrATED......I say the tire routine is less expensive....and easy to change back to normal.

 

I wan this mod BAD. I think I would change the limiter though. Get a custom tune to get the red line pushed ot 7200 RPM's. On an Auto this is a HUGE gain. we have an even taller final drive gear than the 6MT's, so this would be awesome. and why not get better rims and the final drive gear change.

 

Some good points. I'd hate to have the typical 6MT tranny problem, only to have it blamed on the final drive gear replacement.

Still, considering I'm staying NA, this is an attractive mod. I just don't have any idea what the reduction will translate to on the highway. Hopefully I'll know how many revs are turned at 80 in 6th gear by the end of the week (when my G arrives).

 

No.
Click this link for more info.

 

That's encouraging. I think I'll try to chat with Mike at Performance Nissan if I get the time later today. I caught a little blip on him in Road & Track's SPEED magazine, where it mentions he did the mod on a Z.

 

interesting....does this mean switching ride height ..i.e. diameter of wheels will have no negative effect on speedo?

 

Ron I have that Speed article also. Pretty Crazy how his NA modded car runs 1 sec better on the track than the FI cars! Makes me want to go out and get the Tilton Set-up he has.

 

Can anyone scan this article and put it up... what set up does he have holy crap. faster than FI???? That would be awesome. I just want some extra jump off the line, I need this modification bad. I saving up my cash starting today.

 

No. What it is saying is that the speedo is taken from the rear axle outputs after the differential. I'm not sure but I think it uses the ABS shaft encoders, which you can see on both sides of the diff, then maybe averages the 2. Anyway, ground speed will be based on how far your car rolls per revolution of the axle. Changing your rear wheel circumference relative to OEM will affect the speedo.

 

I hope you can read this. If you can I will scan the rest of the article. This is just the track results, then Mike from Perforamnce Nissans Car in the yellow secion.

 

i want this mod really bad also.. im gonna get it here soon. i cant wait

 

my stock 05 G35X auto is already at 3000 rpm's or so on the highway in 5th at around 75 mph. I dont think I would want to be higher than that. I wish the stock 5th gear was a little lower to drop the rpm's to 2500 at 75 mph.

 

"Faster than FI" is a bit misleading. They tested four tuner cars (2 twin-turbo, 2 supercharged) around a road course. The NA 350Z was running sticky race tires, and the tested tuner vehicles were limited to DOT race/street tires. But, the NA 350Z did turn a lap time better than the others.

The NA 350Z that Mike ran had Nismo Y-pipe and exhaust (don't recall if it mentioned cats, but headers weren't mentioned). I don't recall specifics, but the engine mods were minimal bolt-ons. Suspension consited of the Nismo S-Tune package w/ sway bars and Nismo wheels. The big help was the final drive swap AND the sticky-*** tires.

Still, that's pretty good, considering some of the big-money suspensions and 400+HP turbo kits sported by the competition.