VHR + FD Gear Ratio upgrades - 3.9 and 4.08

black09Z · 08-22-2009, 09:21 PM

i wish i knew how to do this, or at least where to go to find out what i should get

Z1Performance · 08-23-2009, 12:21 PM

the 4.08 is without question the one to get. It's a big enough step up from the factory 3.7 that it will provide a noticeable change in acceleration, but without putting the car into some crazy rpm zone on the highway in 6th

Here is how it shakes out vs the stock 3.692 final drive. Tire used for these calculations is the 275/35/19 found in the sport package, and the factory 7500 red line. This is top speed per gear, based strictly on ratios. Obviously wind drag has a huge effect, but for purposes of this discussion it is not taken into account

Stock 3.692
1st Gear 42.36MPH
2nd Gear 69.15MPH
3rd Gear 98.95MPH
4th Gear 126.44MPH
5th Gear 160.7MPH
6th Gear 202.39MPH

4.08
1st Gear 38.33MPH
2nd Gear 62.57MPH
3rd Gear 89.54MPH
4th Gear 114.41MPH
5th Gear 145.42MPH
6th Gear 183.15MPH

As you can see, acceleration per gear will be ~10% quicker per gear, and top speed is reduced by ~10% per gear

Luigi · 08-28-2009, 01:25 PM

So has anyone put the 4.08 into a 370Z Manual Trans?
This would be the best bang for the buck mod!

Imagine a stock Zed with 4.08, HFC and ECU tune.
13-15% acceleration all around in every gear.

javol · 09-07-2009, 09:29 PM

Quote:

Originally Posted by KLRCADI

....yes, this is the same R200 diff in the 350z, G35, G37 (and about a dozen other Nissan cars/Trucks)

Pete

Exactly the same R200 diff?

Here we go with the two OEM Nissan figure:

350Z

370Z

From the images and parts numbers, we can see that 370Z diff comes with 4 satellites..... 350Z with only 2 satellites...

The other components seem to be "more or less" the same...

Any of you can give a reliable tech opinion?

Bye,

NewYorkJon34 · 09-07-2009, 10:45 PM

where can I buy these gears from + whats the price?

Z1Performance · 09-08-2009, 11:22 AM

we offer them, and have tons of 350Z/G35 customers with them over the years

Z-1 Performance Automotive Services Inc. - 4.08 Final Drive for 350Z/G35

NewYorkJon34 · 09-08-2009, 12:34 PM

Wouldn't the 3.9 gear set be better for DD? plus I drive on the highways alot

Z1Performance · 09-08-2009, 06:37 PM

there is a 4% difference between 3.9 and 4.08 - and a $200 price difference, and the nature of waiting for a special order - IMHO, not worth it, but it's a decision you need to make for yourself. Your money but the factory gears being what they are, it isn't worth the price of admission (to me) to swap in ones that are a measly 5% shorter....especially on a car that wants to rev like the VQ. Heck in my car, I run 3.9's now, built NA VQ35, redline at 8400, and I'm swapping them for 4.3's because the 3.9 just is not enough anymore

the 4.08 is perfect for the VQ35HR (2007-2008 350Z), and even more so for the torquier VQ37HR

steven88 · 09-12-2009, 08:54 PM

For those of you familiar with this modification, does it effect the overall speedometer/odometer numbers? Or what about Gas mileage numbers?

And also, I know changing the overall diameter of the rear tires will effect final drive gear ratio as well....stock overall diameter for 275/35/19 is 26.5...what overall diameter tire will be required to achieve the same numbers as 4.08 final drive gear ratio? Just curious thats all...I know some might be interested in changing the tire size instead of dropping the rear differential and opening the gear assembly

NewYorkJon34 · 09-12-2009, 09:04 PM

Would the 4.08 gears be good if my car is a daily driver?

Z1Performance · 09-13-2009, 09:08 PM

Quote:

Originally Posted by steven88

For those of you familiar with this modification, does it effect the overall speedometer/odometer numbers? Or what about Gas mileage numbers?

And also, I know changing the overall diameter of the rear tires will effect final drive gear ratio as well....stock overall diameter for 275/35/19 is 26.5...what overall diameter tire will be required to achieve the same numbers as 4.08 final drive gear ratio? Just curious thats all...I know some might be interested in changing the tire size instead of dropping the rear differential and opening the gear assembly

speed is taken from the ABS sensor so zero issue with the speedometer

I currently have the 3.9 final drive in my 350Z. Stock final drive on the Z33 was 3.54 for manual trans. cars. So, about an 11% difference. My car gets exactly the same mileage with the gears as it did before them - ~320 miles before it needs to be filled. I've driven as far as 14 hours at a clip with them

you could not put a tire on the car that would equate to these gears. Tire changes amount to very small net changes in the final drive.

Z1Performance · 09-13-2009, 09:09 PM

Quote:

Originally Posted by NewYorkJon34

Would the 4.08 gears be good if my car is a daily driver?

there are hundreds of 350Z's using these in normal everyday use

NewYorkJon34 · 09-13-2009, 11:22 PM

^ I've have never installed new gears before, Im just trying to learn about new parts for my 370Z, what would be the benefits of installing the 4.08's? Plus I heard something about the gears would not be good if I drive on the highway alot. I know I prob sound lame, but this is just one part I'm unsure about.

steven88 · 09-13-2009, 11:33 PM

Quote:

Originally Posted by NewYorkJon34

^ I have never installed new gears before, Im just trying to learn about new parts for my 370Z, what would be the benefits of installing the 4.08's? Plus I heard something about the gears would not be good if I drive on the highway alot. I know I prob sound lame, but this is just one part I'm unsure about.

basically it shortens the gearing and allows your engine to be in the power band...longer gear ratios will take longer for your engine RPMs to rise...and when you shift gears, it falls back down further...aftermarket final drive gears modify this and keeps your engine from not falling out of the power band when shifting gears...and also allows it to rise quicker

a competent mechanic should be able to install it for $200-$300

NewYorkJon34 · 09-14-2009, 09:18 AM

Ya I would have my friend who is a mechanic install it for me, so I guess 1st gear would be really short right? Would it be alil pain if you drive on the highway alot? And does it affect the SRM system at all?

08-23-2009, 12:21 PM	#47 (permalink)
Z1Performance Base Member Join Date: Aug 2009 Location: St. James, NY Posts: 237 Drives: 350Z Rep Power: 15	the 4.08 is without question the one to get. It's a big enough step up from the factory 3.7 that it will provide a noticeable change in acceleration, but without putting the car into some crazy rpm zone on the highway in 6th Here is how it shakes out vs the stock 3.692 final drive. Tire used for these calculations is the 275/35/19 found in the sport package, and the factory 7500 red line. This is top speed per gear, based strictly on ratios. Obviously wind drag has a huge effect, but for purposes of this discussion it is not taken into account Stock 3.692 1st Gear 42.36MPH 2nd Gear 69.15MPH 3rd Gear 98.95MPH 4th Gear 126.44MPH 5th Gear 160.7MPH 6th Gear 202.39MPH 4.08 1st Gear 38.33MPH 2nd Gear 62.57MPH 3rd Gear 89.54MPH 4th Gear 114.41MPH 5th Gear 145.42MPH 6th Gear 183.15MPH As you can see, acceleration per gear will be ~10% quicker per gear, and top speed is reduced by ~10% per gear 370zrider and kinitox like this.

09-08-2009, 06:37 PM	#53 (permalink)
Z1Performance Base Member Join Date: Aug 2009 Location: St. James, NY Posts: 237 Drives: 350Z Rep Power: 15	there is a 4% difference between 3.9 and 4.08 - and a $200 price difference, and the nature of waiting for a special order - IMHO, not worth it, but it's a decision you need to make for yourself. Your money but the factory gears being what they are, it isn't worth the price of admission (to me) to swap in ones that are a measly 5% shorter....especially on a car that wants to rev like the VQ. Heck in my car, I run 3.9's now, built NA VQ35, redline at 8400, and I'm swapping them for 4.3's because the 3.9 just is not enough anymore the 4.08 is perfect for the VQ35HR (2007-2008 350Z), and even more so for the torquier VQ37HR Last edited by Z1Performance; 09-08-2009 at 06:43 PM.

09-13-2009, 11:22 PM	#58 (permalink)
NewYorkJon34 A True Z Fanatic Join Date: Jun 2009 Location: Naples, Florida Posts: 3,041 Drives: 09 Fairlady Z Rep Power: 1064	^ I've have never installed new gears before, Im just trying to learn about new parts for my 370Z, what would be the benefits of installing the 4.08's? Plus I heard something about the gears would not be good if I drive on the highway alot. I know I prob sound lame, but this is just one part I'm unsure about. Last edited by NewYorkJon34; 09-14-2009 at 09:20 AM.

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08-22-2009, 09:21 PM	#46 (permalink)
black09Z Base Member Join Date: Mar 2009 Location: killeen tx Posts: 202 Drives: black 09 370Z 6spd Rep Power: 16	i wish i knew how to do this, or at least where to go to find out what i should get

08-28-2009, 01:25 PM	#48 (permalink)
Luigi Base Member Join Date: Jul 2009 Location: Italy Posts: 22 Drives: BMW 325i Rep Power: 15	So has anyone put the 4.08 into a 370Z Manual Trans? This would be the best bang for the buck mod! Imagine a stock Zed with 4.08, HFC and ECU tune. 13-15% acceleration all around in every gear.

09-07-2009, 10:45 PM	#50 (permalink)
NewYorkJon34 A True Z Fanatic Join Date: Jun 2009 Location: Naples, Florida Posts: 3,041 Drives: 09 Fairlady Z Rep Power: 1064	where can I buy these gears from + whats the price?

09-08-2009, 11:22 AM	#51 (permalink)
Z1Performance Base Member Join Date: Aug 2009 Location: St. James, NY Posts: 237 Drives: 350Z Rep Power: 15	we offer them, and have tons of 350Z/G35 customers with them over the years Z-1 Performance Automotive Services Inc. - 4.08 Final Drive for 350Z/G35

09-08-2009, 12:34 PM	#52 (permalink)
NewYorkJon34 A True Z Fanatic Join Date: Jun 2009 Location: Naples, Florida Posts: 3,041 Drives: 09 Fairlady Z Rep Power: 1064	Wouldn't the 3.9 gear set be better for DD? plus I drive on the highways alot

09-12-2009, 08:54 PM	#54 (permalink)
steven88 Base Member Join Date: Aug 2009 Location: Cerritos, CA Posts: 39 Drives: 08.5 mazdaspeed 3 Rep Power: 15	For those of you familiar with this modification, does it effect the overall speedometer/odometer numbers? Or what about Gas mileage numbers? And also, I know changing the overall diameter of the rear tires will effect final drive gear ratio as well....stock overall diameter for 275/35/19 is 26.5...what overall diameter tire will be required to achieve the same numbers as 4.08 final drive gear ratio? Just curious thats all...I know some might be interested in changing the tire size instead of dropping the rear differential and opening the gear assembly

09-12-2009, 09:04 PM	#55 (permalink)
NewYorkJon34 A True Z Fanatic Join Date: Jun 2009 Location: Naples, Florida Posts: 3,041 Drives: 09 Fairlady Z Rep Power: 1064	Would the 4.08 gears be good if my car is a daily driver?

09-14-2009, 09:18 AM	#60 (permalink)
NewYorkJon34 A True Z Fanatic Join Date: Jun 2009 Location: Naples, Florida Posts: 3,041 Drives: 09 Fairlady Z Rep Power: 1064	Ya I would have my friend who is a mechanic install it for me, so I guess 1st gear would be really short right? Would it be alil pain if you drive on the highway alot? And does it affect the SRM system at all?