• Limited Slip Differential

Question

Do I have a VLSD?

Answer 1

I tried the most popular VLSD test while the car was up on a lift. I definitely have the VLSD, confirmed via other means. Namely, big orange sticker on the side that says VLSD.... Anyway, all forms of this test were done with both drive wheels completely off the ground. Here's what I found:

With transmission in neutral, spin one wheel by hand and the other spins the same direction. Both spin very freely.

With transmission in gear (driveshaft fixed), the wheel is much more difficult to spin, plus the other wheel rotates in the OPPOSITE direction.

With one wheel fixed (someone holding it in this case, could also be on the ground), either in neutral or in gear, it is very difficult to turn the other side at all, but it will turn given enough force.

I've heard that other VLSDs and other types of LSDs tend to react to this test differently. For instance, the Torsen and other similar helical limited slip differentials act just like an open differential when subjected to this test. However, the above is how Nissan's R200V VLSD reacts to the test. I'd assume that the Z32's R230V would react the same since it's of similar design, just a bigger ring gear.

Answer 2

-Tony

Question

Whats the difference between posi-traction, and limited slip, any others?

Answer

I think I can take this one. Pretty much posi-trac and limited slip are the same. There are others such as open rearends, locking differentials, and spools. Posi-trac means that both tires are spinning almost all the time. The differential (this is where the limited-slip comes in) has a clutch in it. When both tires get to spinning very quickly (as in loss of traction),  the differential transfers the power to the tire with the most traction. Hence the limited slip name. Good example? Say you have a 240 with about 350 hp. Limited Slip diff. You wind it up to about 5g, and side-step the clutch. What do you get? A lot of wheelspin, and two blackmarks for a while. However, if it keeps on spinning, the differential will sense the loss of traction, and disengage the clutch to whichever side has the least traction. Say the left side is hooking up a hair better than the right side -- it transfers the power to that side so that the left side is pulling, and the right side is just rolling. Open differentials are just that. Both tires are free to spin whichever way they want. However, one tire (usually the right) is the driving wheel. That's where all the traction goes. If you wind it up and dump it, and just one black mark appears, chances are you have an open differential, or you are riding a motorcycle. Locking differentials are pretty cool. There are three types -- speed-sensitive, torque-sensitive, and a Detroit Locker. From the way I understand it, a speed-sensitive diff just spins the right tire, but if it senses that it's spinning way too fast, it will "lock-up" the other tire. So for example, if you wind it up and let it go again, the right tire will spin (one blackmark) for a few feet, and then the diff will realize that there's a loss of traction (the car is not speeding up quite as quick as what the wheel is turning), and it will engage the other axle. Torque-sensing acts pretty much the same way. A Detroit Locker acts kinda opposite. It's almost always locked together, meaning it's driving both tires. However, when  you go into a curve, and one axle is turning faster than the other, it will unlock and start clicking. (They are extremely noisy.) When you exit the turn, it will lock back up and start turning both tires again. They're kinda dangerous in the sense that when they lock-up, if you're not totally out of the curve, they will create some nasty understeer. Lastly is the spool. You've heard of people welding the axles together, well here ya go. Pretty much the axles are locked together 100% of the time. This is only good for drag racing, or driving in a straight line. You can't take a curve effectively because one axle is not free to turn faster than the other one, causing you to "hop" around a curve.  I hope his has answered your questions. If anyone else can correct me or add something different, feel free!

BL

Answer 2

Posi-traction is Chevy's name for a limited slip diff. Like Bandaid, and  Kleenex, the name takes on a generic meaning: a posi rearend is a  limited slip unit.

Question / Answer

Name: Jared Topilko
Email: [email protected]
Subject: L.S.D. installation

Faq:
I have a 240sx without a LSD and would like to have one put in.

Solution:
Get a third member from a wrecked 240sx with a LSD and the back half of the driveshaft from your model 240sx S13 or S14 and replace the parts on your car with these.Replace the oil in the pumpkin with new oil.Any questions e-mail me.