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GENERAL

What is a Final Drive?
The final drive is the final gearing before the rear wheels. The input from the transmission goes into the final drive receiving a final reduction before entering the drive axles. The final drive is made up of a ring and pinion gear and is mounted on the rear differential.

What is the OEM final drive ratio?
The 5spd automatic has a 3.357 final drive ratio.

The 6spd manual has a 3.538 final drive ratio.

Are there aftermarket final drives?
Yes. Currently only a 3.917 ratio gearing is available and is offered by several companies.

How can changing it help?
There are two options here based on need.

1. Going up in ratio gearing improves acceleration. (i.e. 3.3 ---> 3.5 ---> 3.9) This is generall NOT recommended for forced induction vehicles. Those who have done this in conjunction with FI have noted that first gear becomes worthless in 6spd tranny cars.

2. Going down in ratio gearing can improve traction and widen the gears for high power applications (i.e. 3.5 ---> 3.3) This is generally NOT recommended for naturally aspirated or lightly modded vehicles. It can severaly slow down the accelleration.

Can I put one in my 5spd automatic?
It is not recommended to install the 3.9 gears into an automatic. However, many owners have had success installing the 3.5 gears, improving acceleration.

Why is the 5spd automatic final drive different?
Because the transmission has few gears and each is gear has a different ratio than the 6spd manual counterpart. In short: the 3.3 gear is the appropriate OEM gearing for the 5spd, just as the 3.5 is the appropriate OEM gearing for the 6spd.

WIll it work with the XXXX LSD?

Is this a good modifcation for FI'd cars?

Is this a good mod for the drag strip?

What is the top speed with the final drive changed?

What final drive ratios are available?

3.3: This is the standard final drive gearing that comes with the 5spd automatic transmission.

3.5: This is the standard final drive gearing that comes with the 6spd manual transmission.

3.9: This is the popular after market gearing for the 6spd manual.

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INSTALLATION

How much does it cost to install?
Installation prices range from 300 to 600 depending on who you ask. Keep in mind you may need additional parts. See the Final Drive Wiki Page for more information on this.

What extra parts are needed?
(LINK)

Can I install this myself?
Only you can answer that. If you are asking this question then probably no. This installation requires some special tools. You have to drop the entire pumpkin assembly down from the chassis and I have heard that requires some of the rear suspension to be removed as well.

Is there an installation tutorial?
not yet.

How long does the installation take?
It would be possible to do in a single day for someone who has all the right tools and is experienced. However expect at least 2 days and even longer if extra parts are required once the pumpkin is open.

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MAINTENANCE ETC..

I hear funny noises after the install.
It may be ok to hear some noise, but too much noise means something could be wrong. The most likely cause is an incorrectly shimmed gear set.

Will this affect my gas mileage?
It has the potential to affect it, but not by too much.

Will this affect the TCS/VDC?
No.
 

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a question no one seem to ask is if the speedometer will not give the right reading due to gear cahnge and is there a quick fix to this problem.
 

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a question no one seem to ask is if the speedometer will not give the right reading due to gear cahnge and is there a quick fix to this problem.

The speedometer reads from the axle. There will be no error in the reading (except the error that is already built in)
 

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Is this a typo?

Can I put one in my 6spd automatic?
It is not recommended to install the 3.9 gears into an automatic. However, many owners have had success installing the 3.5 gears, improving acceleration.
 

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It would be intresting if someone had run quarter mile times before and after in instal to let us know how it effected it. Conversly it would also be intresting to here about before and after track times. I have a feeling on a tight track it would make the most improvement?
 

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I saw on the wiki page Nissan makes a 3.7 drive. Is this something that would work a little better with lightly boosted cars? I say tha you said high hp engines work poorly with 3.9 because first becomes worhtless.
 

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I saw on the wiki page Nissan makes a 3.7 drive. Is this something that would work a little better with lightly boosted cars? I say tha you said high hp engines work poorly with 3.9 because first becomes worhtless.
I think it is all in the driver, the overall setup of the car, and its usage. Mines R34 runs a 4.2 final drive with 600-700hp.

With a boosted car and lowering the gearing, you are making 1st gear useless. But if you are on a road coarse you will never be in first gear anyways.
 

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I think it is all in the driver, the overall setup of the car, and its usage. Mines R34 runs a 4.2 final drive with 600-700hp.

With a boosted car and lowering the gearing, you are making 1st gear useless. But if you are on a road coarse you will never be in first gear anyways.
Good point. Something to consider for sure!
 

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Is anybody here experienced doing rear end setup? I am getting towards the end of a Quaife LSD/4.083 gear upgrade on my base model '05 and would like to share pics of the gear marking pattern I am getting to see if I should run it or remove some pinion shim.
Maybe PM me if you guys don't want it in this thread.
thanks!
 
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