speederx7@yahoo.com

What are pros and cons of each. I have a 90turbo and an 86 NA LSD. Just curious. Are there diffrences between response or size between the two. Also are the stock ones 1, 1.5 or 2 way? Im assuming 1.5

Node

iTrader: (1)

This is only how I've udnerstood it, I could be wrong

VLSD is kind of on/off
Clutch is more predictable

VLSD can last a long time by just changing the fluid on time
Clutchs will burn out and cost almost $400 for new ones, I think I've seen from 50-80k they start losing there use as limited slip.

I have no idea on if they are 1, 1.5, or 2 way.
My guess would be one way.

No7Yet

Clutch-type diffs have a much quicker engagement, whereas the viscous tend to require a few spins before they'll lock up. Clutch-pack diffs also tend to lock up a little bit better, and can hold more power. Since there's no direct mechanical connection in a viscous diff, too much torque can burn them up quick. That said, clutch packs tend to wear out in as little as 30k miles, due to the nature of their friction plates. Mechanical wear's a bitch.

With all that in mind, you're comparing apples and oranges. The TII diffs are all much stronger than their N/A LSD counterparts, especially when considered with their thicker halfshafts and the TII's thicker driveshaft. Your clutch-pack diff is probably already worn out, as well, while the viscous unit is almost as good as new with a fluid change...

Oh, and node? you've been playing too much GT3.

Brandon

Node

iTrader: (1)

<---badass FC dorifto king in GT3

speederx7@yahoo.com

How the hell do you tell if the clutch pack is going bad? Im using close to stock HP. Ive heard the Clutchs go quicker in High HP like dragging. Why do you think Viscous is less predictable. Isnt the LSD on/off anyways.
On=accel off=deccel Im think drift purpose. So is a clutch "more predictable" because it can slowly engage? Wouldnt this be like slipping you clutch, dramaticlly reducing the life of the pack?
Im just wondering.
Can KAAZ and Cusco 2ways fit in the NA LSD?

No7Yet

The best way to tell whether a clutch-pack LSD is going bad is to slap it on a car, and do a burnout with one wheel on wet grass and the other on dry pavement. If you get a nice black strip on the pavement, the LSD is still good.

Clutch LSDs only wear when they're partially engaged, like when turning and accelerating or at the start of a donut.

If anything, VLSD is more predictable, since it's action is less binary. It gives you a moment of push before the outside wheel locks up. On the street, that's nice.

A clutchpack LSD is nicer on a road course, though, because you've most likely got very stick tires that you're not going to be able to break loose (on the outside) just with torque. In this case, you want your diff to lock up as quickly as possible (in most cases about 1/2 turn) to maximize exit speed.

Drift setups have nothing to do with real road course or autocross setups. Don't confuse the two

You'll have to ask KAAZ and Cusco.

Brandon

MechE00

Umm.. wouldn't the _inside_ wheel be the one to start spinning first? or am I misunderstanding your use of the term "locks up"?

Hot_Dog

Viscous LSD works similar to a torque converter on an AT. A viscous coupling, a sealed unit containing silicone fluid, serves to couple both drive wheels together. Since viscous LSD uses a fluid coupling the bias ratio of the differential is nonlinear, which means that the differential behaves as an open differential when starting out and gradually transitions into a LSD as crusing speed is reached.

The advantage of the viscous LSD is that additives are not required, and the viscous LSD also tends not to lockup the rear wheels when decelerating, which is a good thing when you're on a slippery surface such as ice. A disadvantage is that the viscous coupling is not repairable -- should it leak, than you got to buy a new differential from Mazda.

Friction disk LSD couples both wheels together through a series of alternating friction disks and steel disks compressed together by a spring. When making a turn, the differential action of the drive wheels will cause the friction disks to slip as they are clamped between the steels disks. The tighter the spring, the less the tendancy of the friction disks to slip. If the spring is extremely strong, than the differential may approach that of a locking differential. Racing applications usually demand a strong clamping force, which leads to a high bias ratio. The friction disk LSD has a linear bias ratio, and will exihibit LSD characteristics at start-off speeds. The slope of the bias ratio line is, I believe, the number that you are referring too. One disadvantage of clutch type LSD is that (especially for high bias ratios) if the driver decelerates on a slippery surface such as ice, than controlling the car tends to become a bit dicey.

Friction disk LSDs may require a friction modifing oil additive to prevent chatter, which is usually at its worse when starting off and making a turn at the same time. Also, friction disks do wear out over time and will eventually need to be replaced. When do they need to be replaced? Well, with one wheel on the ground an othe other raised, it should require a reasonable amount of effort to rotate the opposite wheel. It's hard to describe, but it should feel as if the e-brake is partially applied. Chrysler (at least during the 60's and 70's) used to specify a turning torque to determine if the friction disks need to be repalced. That is, with one wheel on the ground and the other raised, a torque wrench is used to rotate the raised wheel. If the torque does not meet the specified value, than the clutch plates need to be repalced. With Mazda, unfortunately you have to dissemble the rear end and inspect (i.e., measure thicknesses ?) the clutch plates. I would guess that their lifetime would probably be comparable to that of clutch & pressure plate, under "normal" driving conditions. Do RX7 owners know about "normal" driving conditions?

BTW, the TII differential is a lot "beffier" than the NA, and it will consequently withstand much more abuse.

On another note, the 3rd and some Miata's use a Torsen or torque sensing type differential, which uses the action of worm gears to couple both driving wheels. I don't know much about it, but hear that it's much better than either of the two types discussed above.

Hot_Dog