any idea what the raised rpm's would be (at say, 60mph in 6th gear)???

a couple hundred higher, or 1K higher???

i still like this idea, even if its more shifts down the ¼ (which im not doin anyway)

 

any idea on how bad the gas mileage will be?

 

Its in this forums archives somewhere. Gas mileage wast effected that much either. Right now I have techno reflash, 350EVO t body,Injen CAI and Injen exhaust and I am at 20.3. I wanna say I was at 19.8 with the final drive but I cannot remember for sure. Looking back at some of the data from our race car when we tested it out....you def rev throught the gears faster.

 

copied from old thread........
"Its right about 3075-3100 RPM"
60 mph.

 

my stock final gear 6mt goes 80 mph @ 3000 rpm in 6th gear. dropping to 60 mph at 3000 rpm seems like a lot...

 

That was 60 mph in 5th gear is 3075-3100 RPM with the 3.9 final drive.

 

If someone decides to get this installed, please try and get 0-60 and 1/4 times before and after.

 

I believe there will be better 0- 100 times than 0 - 60.

 

How much??

 

Retail $899.95

 

Wonder if this would hurt or help a turbo setup, since you generally want the boost to last as long as possible...

 

You usually want longer gears for a turbo.

 

that sounds much better

 

with stock 6mt final drive, 60 mph in 5th gear was at 2800-2850.

 

This is more of a mod for road courses and tracks. It's not a great mod for the 1/4 mile, or for daily driving. It's a fairly cheap acceleration mod, but I think $900 is not worth it if you just want to make your car faster for no special reason. Obviously if you track your Z, go for it.

0-60 times are not going to really improve because of lack of traction Of course a new LSD and some slicks would help that.

 

I'll definitely do a before and after. Right now I've got 295 Toyo's, ECU, Y-pipe and pulley and run 5.25-5.5 sec 0-60. Those times are with a data logger.

 

I would say 3rd through 6th will have more of an impact with this modification that 1st through 3rd. On road courses it will help do away with going down to second or being caught between 2nd and 3rd gear. Third will accel much better.

 

Going to a 3.9 ratio will increase RPMs at speed by 11.4%. You'll have 11.4% more torque to the road at any given RPM, and you'll be operating higher up the engine torque curve at any given speed, up to the 4800 RPM torque peak on a stock engine. That all means quicker acceleration, provided you can maintain traction. The car will feel a lot "peppier" in each gear as you drive around town (unless you normally drive with the engine wound tight around town, then you won't see much change).

OTOH, speed at redline in each gear will be 11.4% lower. That'll make our already ridiculously low first gear even more useless, though it will make second a better "first" gear. As far as top speed is concerned, that'll still be over 140 MPH at redline, and that's plenty fast enough for all but the longest tracks.

Changing the final drive won't affect the speedometer on our cars since that's derived from wheel sensors. The load on the tranny at any given speed will actually be the same or lower, depending on how hard you press the loud pedal. But the torque our half shafts will see will be higher. On a highly modified car, this could lead to twisted or broken axles. Gas mileage will be hurt when driving "economy" style, you can forget about seeing 27 MPG. But if you drive enthusiastically anyway, there probably won't be much of a change.

 

thanx 4 the info

 

It does make good since to upgrade the LSD to the NISMO LSD while you have the differential down and add the 3.9 final drive. My question is does anybody have a sound clip of the Nismo LSD making the poping sound. I have never heard one and wondering if its streetable(ie daily driving) or just track worthy.