Limited Slip Differentials (LSD)

From Nissan 350Z & 370Z Wiki

A Limited Slip Differential, or LSD, is a differential having special friction mechanisms tending to keep both rear-axle shafts rotating at the same speed, regardless of unequal tire-to-road surface friction. The G35 Coupe and all but the Base model 350Z come with a viscous LSD.

Also see: Limited Slip Differential (FAQ)

Contents 1 Aftermarket LSD Options for the 350Z 1.1 Carbonetics (ATS) 1.2 Cusco Type MZ 1.3 Cusco Type RS 1.4 KAAZ 1.5 Nismo 1.6 OS Giken 1.7 Tomei 1.8 Quaife 2 Differential Overview (Gear vs Clutch Type) 3 Wikipedia 4 Types 4.1 1 Way 4.2 1.5 Way 4.3 2 Way 4.4 Mechanical 4.5 Viscous

Below you will find all the currently available LSDs for the 350Z and G35. Each LSD is designed different, so look over the specs and prices and choose which is best for you. If you have questions you can visit our drivetrain forum.

Aftermarket LSD Options for the 350Z

Carbonetics (ATS)

ATS

List:
Found: $1299
Type: 1.5 way
Engagement: Carbon Clutch
Notes: Chrome molybdenium steel housing and gears

Cusco Type MZ

Cusco

List:
Found: $875
Type: 1.5 or 2 way
Engagement: clutch

Featuring high tension chrome molybdenum steel housing and gears the Cusco LSD is up for the task of serious competition. With large oil windows for increased flow and Cusco's original groove cut technology for improved efficiency on the clutch plates, stability and longevity is promoted. The 1.5-way Type MZ utilizes cone plates to develop the initial torque and features full engagement during acceleration and partially under deceleration.

Cusco Type RS

Cusco

List: $1182.60
Found: $1065
Type: 1.5 or 2 way
Engagement: Coil Springs

Low power loss means better lap times for even the mild tuned of cars. Chattering is kept low. Improved durability as clutch plates are low pressured. The LSD efficiency is higher with smoother oil flow between plates. According to CUSCO'S in house research, initial torque is 50 to 70% lower compared to the conventional cone plate type LSD enabling lower drive friction and better response.

Special precision springs, set in the pressure plate, assure steady coil movement. Clutch plates do not stick together like conventional cone plate type LSDs. Therefore less clutch plate wear or deterioration occurs.

The Type RS LSD had proved to be capable of competition use in the All Japan Gymkhana Championship without overhauling a single time during the season. With all drivers and teams finishing with good or championship results at the end of the season.

KAAZ

KAAZ

List: $995
Found: $845
Type: 2 way
Engagement: Clutch

Nismo

Nismo

List: $1045
Found: $939
Type: 1.5 or 2 way
Engagement: Clutch
Notes: 3 stage initial torque selective (60%/80%/100%) can be adjusted without disassembling the LSD

The Nismo GT LSD is a 1.5 way (upgradeable to 2 way) limited slip differential designed to provide maximum traction that is most often lost in hard off-the-line acceleration. The unit will sense when one wheel starts losing traction due to track/road conditions, hard cornering, and/or torque steer. Once it detects the slippage, it will compensate by shuffling the power from side to side to overcome the loss of traction. This translates into better track or quarter mile times, and more efficient use of the engines power. On the 350Z/G35 the rear LSD is adjustable in 60%, 80%, and 100% lockup mode. This LSD is VCD compatible (although you will have to turn VCD off to enjoy the full benefits). The Nismo GT LSD is a full install kit, including everything shown, and is perfect for the base model 350Z adding an LSD.

• Clutch-Type Design with 10 clutches on each side
• Constructed with four pinion gears for improved strength (stock LSD has two pinion gears)
• 3-stage initial torque selective adjustable without disassembly
• Plate-type 1.5-way LSD can be converted to 2-way LSD
• Compatible on all 350Z & G35 Manual Transmission (with or without stock LSD
• Compatible on 350Z & G35 Automatic Transmission when upgraded Final Drive gear is used (3.5, 3.7, 3.9)

Benefits:

• Designed as a multipurpose LSD for city driving
• Increased power for track or autocross conditions

Included:

• NISMO LSD
• 2 x Output Shafts
• 2 x Differential Side Oil Seals
• 2 x Differentail Side Bearings
• Differential Bolts
• Instructions
• Differential Oil

OS Giken

OS Giken

List:
Found:
Engagement:

Tomei

Tomei

List: $990
Found: $839
Type: 1.5 or 2 way
Engagement: Clutch
Notes: For 350Z/G35 with factory Viscous LSD

Quaife

Quaife

Part Number: 44.309.181
List:1495
Found: $1313.99
Engagement:Gear
Notes: The Quaife differential is a drop in installation for the "open" diff base model 350Z or G35 6MT. If you have the factory Nissan VLSD, you will also need a set of stub axles from a base model open diff 350Z. Nissan P/N 382200 AR000 Axle Flange

Differential Overview (Gear vs Clutch Type)

The hypoid style works off of the torque actually being applied to the ground from the faster spinning wheel, while the clutch style keys off the torque spinning through the axle of the faster wheel.

Quaife is a mechanical diff that uses hypoid gears to bias the torque between the 2 wheels. The gear designs creates internal torque multiplication based off of the torque applied to the ground from the wheel with the least resistance. Quaife biases torque only under acceleration.

The ATS is a clutch style differential. I'm not sure what the lockup % is on it, but as one wheel spins faster than the other in a given situation, the pre-loaded clutch mechanism will engage and that % of torque applied to the spinning faster spinning axle will be applied to the side with traction. The ATS is a 1.5/2 way diff so it will lockup and transfer torque under acceleration and deceleration.

So take this for example: Your car generates 200 lb-ft at the wheels. So that's 100 lb-ft of torque to each axle under ideal conditions and that power is being applied to the road surface. As one wheel starts to slip and spin faster, more power starts to go through that axle, and less of it is being transferred to the ground, ie, 150 lb-ft is going through the spinning axle and only 50 lb-ft is being applied to the ground. The rest gets lost as wheel spin. With an open diff, you'd only have the other 50 lb-ft of axle torque being applied to the wheel with traction.

The Quaife uses its internal bias ratio (say 5:1) to multiply the torque actually being applied to the ground of the spinning wheel to the axle with traction. So 5 x 50 = 250 lb-ft. Since you only generated 200 lb-ft up front, you can't bias that much, but you bias 150 lb-ft (200 total potential - 50 of what is actually getting to the ground) to the other side. This is almost an extreme example because the moment you get away from the 50/50 split, the Quaife starts biasing torque instantly. The only downside to this design is if one wheel has no resistance; ice, wheel in the air, etc... Zero x anything is zero, nothing to bias. Why some people pan the Quaife as a track diff.

In the above situation, the ATS would work differently than the Quaife. As power is applied and the clutches lock, the lockup ratio kicks in, say 60%. So as one wheel starts to slip and spin faster, the other wheel will be at least 60% as fast, or gets 60% of the power applied to that faster spinning axle. If the lockup ratio is too high, in low speed turns, you will get tire drag as the clutch locks and the inner and outer tire are too varied in speed.

Couple other key points. Quaife is zero maintenance and has a lifetime warranty, even with track use. ATS claims longer life than metal clutches, but those carbon clutches will still eventually lose effectiveness, particularly if tracked aggressively and requires more maintenance with more frequent oil changes.

I consider both to be the best of their respective designs. But if you have a street driven vehicle and want unobtrusive action, get the Quaife. If you plan to do some serious track events and are OK with the extra maintenance, give the ATS a look. If you have the open diff, go Quaife, if you have the VLSD, I'd lean towards ATS for ease of install. For reference, I had the VLSD, now I have the Quaife. Very happy with it. Probably the best option for street is the Quaife. ATS is best for hardcore trackers.

Nismo is like the ATS, except for metal clutch packs, which is another story in terms of operation and effectiveness. Its not nearly as smooth or quiet.

VLSD is an open diff that uses a viscous coupling. Its facing gears from each axle side in a semi-solid liquid. So when one side starts to spin, the internal gear on that side spins faster. The fluid reacts to the movement, and causes the facing gear to spin, transferring power to the slower spinning wheel. Its a quiet, non-servicable design. Only engages with wheel spin and transfers maybe 25-40% of the power. With high power setups, the viscous fluid can get cooked and get too thin, affecting its ability to transfer the power through the gearing. Its popular for OE use because there is no noise and its transparent under normal driving, but in situations with wheel spin, it engages just enough to be useful.

Wikipedia

Source: http://en.wikipedia.org/wiki/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 an 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.

The main advantage of a limited slip differential is found by considering the case of a standard differential where one wheel has no contact with the ground at all. In such a case, the contacting wheel will remain stationary, and the non-contacting wheel will rotate at twice its intended velocity – the torque transmitted will be zero and the vehicle will remain stationary. In everyday use on typical roads, such a situation is very unlikely, and so a normal differential suffices. For more demanding use however, such as driving off-road, or for high performance vehicles, such a state of affairs is undesirable, and the LSD can be employed to deal with it. By limiting the velocity difference between a pair of driven wheels, useful torque can be transmitted as long as there is some friction available on at least one of the wheels.

Types

Two main types of LSD have been generally used – mechanical (geared or clutch-based) and fluid based (viscous). The latter is gaining ground especially in modern all-wheel drive vehicles, and generally requires less maintenance than the mechanical type.

1 Way

A 1-way notch is cut like an upside down triangle. While the cam can push backward against the tapered edges, expanding the casing, it cannot push forward against the flat surface. Therefore under acceleration torque (cam rotating backwards) it will lock, and under deceleration torque, when the cam is forced to rotate forward due to forces from braking, engine braking, etc.. it will just contact a flat "wall" and the casing will not expand.

1.5 Way

A 1.5-way notch is like an upside down triangle with a half triangle on top of it. During acceleration it will expand the casing at one rate, and during deceleration, it will still expand the casing, but due to the cuts' higher angles, it will require more force to move the casing apart. Therefore, only during Very hard braking will it have enough force pushing it forward to expand the casing.

2 Way

A 2-way notch is shaped like a diamond. It requires almost the same amount of acceleration or deceleration to force the casing apart. Usually, the top cuts are slightly more dramatic, forcing the 2-way to require slightly more deceleration force to push the cam to expand the casing.

Mechanical

In the mechanical clutch type, a mechanism, such as a centrifugal weighted rotor, detects differential wheel velocity and applies friction to the clutch mechanism which links the two shafts together. As the differential wheel velocity increases, more friction is applied. This mechanism forms a negative feedback loop which limits the slip to a preset degree. In some designs, the clutch is self-actuating and oftentimes small multi-plate clutches are used. Because the slip-limiting action (increasing friction) occurs quite rapidly, this method can create unsettling dynamic effects for the vehicle as a whole.

In this case, the use of the word mechanical implies that the limited slip differential is engaged or not due to interaction between two (or more) mechanical parts. This category includes clutch and helical limited slip differentials. For road racing, many prefer a helical limited slip differential, because it does not lock the two output shafts to spin at the same rate, but rather biases torque to the wheel with more grip by up to 80%.

Clutch limited slip differentials use a center cam that moves within a casing as the torque changes. The casing is made up of two symmetrical left and right segments. However, the cuts in the casing making the notches for the cam to slide in are not. That determines 1, 1.5, or 2-way LSD. As the cam slides in the notch, it pushes the casing outward, engaging a series of clutch discs--some attached to the casing, some to the output shafts. When engaged, both output shafts will rotate at the speed of the casing, making both axles and subsequently both wheels, rotate at the same speed.

The more the casing expands, the more clutches contact each other, hence the more the output shafts get locked into the same rotation. Some manufacturers produce adjustable clutch limited slip differentials whereby you may set a breakaway torque level. Resultantly, the clutch discs are moved closer together or further apart to dictate the SOFT, MED, or HARD setting. The closer the clutch plates are to each other, the more readily the output shafts--thus the wheels--will spin in sync.

Geared, torque-sensitive mechanical limited slip differentials utilize planetary gears to "sense" torque on one shaft. The most famous version is the Torsen differential invented by Vernon Gleasman in 1958, then sold to Gleason Corporation, who started marketing it in 1982. Geared LSDs are less prone to wear than the clutch type, but some have found their torque distribution characteristics to be less than ideal.

Viscous

The viscous type is generally simpler, and relies on the properties of a dilatant fluid – that is, one which thickens when subject to shear. Silicone-based oils are often used. Here, a chamber of fluid rotates with the normal motion of the output shafts, but a differential motion causes paddles or vanes to move through the fluid. The greater the speed of the vanes, the more resistance the fluid will put up to oppose this motion. In contrast to the mechanical type, the limiting action is much softer and more proportional to the slip, so for the average driver is generally much easier to cope with.

Viscous LSDs are less efficient than mechanical types, that is, they "lose" some power. However, they are less prone to breakdown as long as the fluid is changed regularly.

Drivetrain

This page is part of the Drivetrain category. To learn more about related items click the links below. Components: Clutches • Drivetrain Accessories • Final Drive Gear Sets • Flywheels • Short Shifters FAQs: 5spd Automatic Transmission • 6spd Manual Transmission • Clutch (FAQ) • Drivetrain Definitions • Final Drive (FAQ) • Flywheel (FAQ) • Limited Slip Differential (FAQ) Tutorials: Automatic Shift Knob Swap • Automatic Shifter Removal • Automatic Transmission Fluid Replacement • Clutch Adjustment • Clutch Installation • Manual Transmission Fluid Replacement • Rear Differential Fluid Replacement • Shift Knob Removal and Replacement • Wheel Stud Replacement