From Nissan 350Z & 370Z Wiki
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This article is part of our special
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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.
- 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.
- 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?
- For lightly boosted setups, the gears can add additional performance while keeping your engine safe. Instead of risking a fatal engine failure, you could achieve the greater acceleration with a gear change. However, as you increase boost levels there comes a point where lower gearing would be more beneficial allowing you greater range in each gear to fully reap the benefits of a high horsepower engine.
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.
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?
- need info....
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.
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.
Drivetrain Definitions
Axle
- An axle is a central shaft for a rotating wheel or gear. In some cases the axle may be fixed in position with a bearing or bushing sitting inside the hole in the wheel or gear to allow the wheel or gear to rotate around the axle. In other cases the wheel or gear may be fixed to the axle, with bearings or bushings provided at the mounting points where the axle is supported.
Clutch
- A clutch is a subcomponent of an engine's transmission designed to allow engagement or disengagement of the engine to the gearbox or whatever apparatus is being driven.
- The coupling mechanism used on a mechanical power press to couple the flywheel to the crankshaft, either directly or through a gear train.
Differential
- A set of mechanical gears that eqaulises the power between the left and right drive wheels, particularly when cornering, when the outside wheel travels further than the inside wheel.
- A device - usually made of gears - that divides the torque between the driving wheels and permits the wheels to turn at different speeds. This is especially important when negotiating a corner, as the inside wheels turn more slowly than the outside wheels.
- A unit that takes the power of the rotating driveshaft at right angles to the rear axle and passes it to the axle. It will not only drive both rear axles at the same time, but will also allow them to turn at different speeds when negotiating turns. In this way the tires do not scuff or skid.
Driveshaft
- A driveshaft or driving shaft is a mechanical device for transferring power from the engine or motor to the point where useful work is applied. The 350Z incorporates a one-piece driveshaft which is actually carbon fiber reinforced plastic.
Final Drive
Flywheel
- A relatively large and heavy metal wheel that is attached to the back of the crankshaft to smooth out the firing impulses. It provides inertia to keep the crankshaft turning smoothly during the periods when no power is being applied. It also forms a base for the starter ring gear and, in manual transmission, for the clutch assembly. Also see engine flywheel and fluid flywheel.
- This is a large gear mounted to the back of the crankshaft which turns the engine when the starter is cranking.
- A flywheel is a heavy rotating disk used as a repository for angular momentum. Flywheels resist changes in their rotation speed, which helps steady the rotation of the shaft when an uneven torque is exerted on it by its power source such as a piston-based, (reciprocating) engine, or when the load placed on it is intermittent (such as a piston-based pump).
Gearbox
- A casing for gear sets that transmit power from one rotating shaft to another. A gear box has a number of functions: it is precisely bored to control gear and shaft alignment, it contains the gear oil, and it protects the gears and lubricant from water, dust, and other environmental contaminants. Gear boxes are used in a wide range of industrial, automotive, and home machinery.
- The shell (metal casing) in which a train of gears is sealed.
Gear Ratio
- The number of revolutions a driving (pinion) gear requires to turn a driven (ring) gear through one complete revolution. For a pair of gears, the ratio is found by dividing the number of teeth on the driven gear by the number of teeth on the driving pinion gear.
- A gearbox contains several toothed wheels that are connected and disconnected to each other in order to switch into the intended gear. The gear ratio is the ratio between the number of teeth of the two wheels that are connected at a given time. If one wheel has 25 teeth and the attached one has 50, there is a 2:1 ratio.
Limited Slip Differential
- A Limited Slip Differential (LSD) is a modified or derived type of differential gear arrangement that allows for some difference in rotational velocity of the output shafts, but does not allow the difference in speed to increase beyond a preset amount. In a car or automobile, such limited slip differentials are sometimes used in place of a standard differential, where they convey certain dynamic advantages, at the expense of greater complexity.
Pumpkin
- The rear pumpkin, or carrier, houses the final drive gears and differential.
Short Shifter
Toe
- Toe relates to the difference in the distance between the front of the tires and the rear of the tires on the same axle, or to the vehicle centerline. Toe-in, or positive toe, is defined as the front of the tires being closer together than the rear of the tires. Toe-out, or negative toe, is when the rear of the tires are closer together than the front of the tires. Zero toe is when the tires are parallel to each other.
- Effects of Toe: Excessive toe increases tire scuffing and results in tire wear and drag on the vehicle. Excessive toe-in, or positive toe, increases scuffing on the outside of the tire. Excessive toe-out, or negative toe, increases scuffing on the inside of the tire, and in some cases can cause a darting or wandering problem. Bias or bias-belted tires will commonly show a featheredge or saw-tooth toe wear pattern across the entire tire tread area. Any tire wear pattern caused by a toe condition can be further affected by an excess camber condition and may result in irregular wear patterns.
