VHR + FD Gear Ratio upgrades - 3.9 and 4.08

Z eliminator · 08-06-2009, 08:58 AM

I changed the diif on my 7 AT to a 4.08 gear set up. The rev matching in city driving takes some getting use to. It uses to turn 2100 at 100 km. Now it turns 2750 at 100.
Fuel consumption went from 7.8 up to 8.7 L / 100 km. I took it to the track and it ran a best of 13.201. Average pass was 13.32 to 13.43. The colder the moter the faster it goes.Going down the track i shifted at 7400 and the RPM only drops to 6300. I have to put in 5th. On the 13.201 pass i hit the limiter in 4th as i tried to make the pass in 3th
It ran at 102.8 mph in that pass. Mt best trap was a 107.9.
The only mod is a stillen G3 intake. Base line was 266 and 286 RWHP after the intake.
The next Z drag day is in Septmeber and it will have a stillen CBE. Berk cats, Stillen headers and the underdrive pully. It should run 12.8 on the 19 inch wheels. Its hard to hook the bridgestones. Best 60 ft 2.01 to 2.09.

wstar · 08-06-2009, 09:06 AM

Z Eliminator: How's the 1-2 shift with the 4.08? Given the slight input lag clicking the button, and how fast the car rips through first gear, I'm worried that a better gear ratio is going to make timing the 1-2 shift nearly impossible.

Minicobra1 · 08-06-2009, 10:27 AM

Quote:

Originally Posted by Z eliminator

I changed the diif on my 7 AT to a 4.08 gear set up. The rev matching in city driving takes some getting use to. It uses to turn 2100 at 100 km. Now it turns 2750 at 100.
Fuel consumption went from 7.8 up to 8.7 L / 100 km. I took it to the track and it ran a best of 13.201. Average pass was 13.32 to 13.43. The colder the moter the faster it goes.Going down the track i shifted at 7400 and the RPM only drops to 6300. I have to put in 5th. On the 13.201 pass i hit the limiter in 4th as i tried to make the pass in 3th
It ran at 102.8 mph in that pass. Mt best trap was a 107.9.
The only mod is a stillen G3 intake. Base line was 266 and 286 RWHP after the intake.
The next Z drag day is in Septmeber and it will have a stillen CBE. Berk cats, Stillen headers and the underdrive pully. It should run 12.8 on the 19 inch wheels. Its hard to hook the bridgestones. Best 60 ft 2.01 to 2.09.

Which model did you end up putting in, what was part#, cost, etc. Also, how is drivetrain noise now, is it much louder, or pretty much the same?

thanks!

javol · 08-21-2009, 12:50 PM

Quote:

Originally Posted by Z eliminator

I changed the diif on my 7 AT to a 4.08 gear set up.

Did you change the whole diff?

Putting on a 350Z (R200) diff with an upgraded 4.08 ring-pinion couple??

It seems this is the only way to move to 4.08 a 370 7AT.

At mynismo.com told me that 4.08 set (Ring & Pinion) for 350Z does not work in 370Z 7AT diff... (that is a R205).

Any other experiences or suggestions?

I'm a bit lost...

Thanks,

Gianni

javol · 09-21-2009, 08:28 PM

Quote:

Originally Posted by Z eliminator

I changed the diif on my 7 AT to a 4.08 gear set up.

What do you change exactly?

Do you install an aftermarket 350Z ring-pinion couple or what?

Thanks!

08-06-2009, 09:06 AM	#2 (permalink)
wstar A True Z Fanatic Join Date: Mar 2009 Location: Houston, TX Posts: 4,024 Drives: too slow Rep Power: 3596	Z Eliminator: How's the 1-2 shift with the 4.08? Given the slight input lag clicking the button, and how fast the car rips through first gear, I'm worried that a better gear ratio is going to make timing the 1-2 shift nearly impossible. __________________ 7AT Track Car! Journal thread / Car setup details

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08-06-2009, 08:58 AM	#1 (permalink)
Z eliminator A True Z Fanatic Join Date: Jul 2009 Location: Ontario Canada Posts: 1,660 Drives: 370 Z 7AT Sports Rep Power: 20	I changed the diif on my 7 AT to a 4.08 gear set up. The rev matching in city driving takes some getting use to. It uses to turn 2100 at 100 km. Now it turns 2750 at 100. Fuel consumption went from 7.8 up to 8.7 L / 100 km. I took it to the track and it ran a best of 13.201. Average pass was 13.32 to 13.43. The colder the moter the faster it goes.Going down the track i shifted at 7400 and the RPM only drops to 6300. I have to put in 5th. On the 13.201 pass i hit the limiter in 4th as i tried to make the pass in 3th It ran at 102.8 mph in that pass. Mt best trap was a 107.9. The only mod is a stillen G3 intake. Base line was 266 and 286 RWHP after the intake. The next Z drag day is in Septmeber and it will have a stillen CBE. Berk cats, Stillen headers and the underdrive pully. It should run 12.8 on the 19 inch wheels. Its hard to hook the bridgestones. Best 60 ft 2.01 to 2.09.