LSD questions!

[Jeff240sx]

Ok.. I had some questions on LSDs.
So far as I know, there are 4 different types of LSD.
Viscous - Uses Silicon material that heats up between plates and expands, locking both half-shafts. Takes a long time to engage.

Mechanical - KAAZ, ect. Uses gears and teeth and is noisy. How the hell does that work without keeping the tires locked all the time?!?

Clutch - Dunno what brands... but uses clutch engagement to lock the tires together. What makes the clutch engage?

Helical - ???. How does this work? I know it's "better" than a vlsd. Also, since the s15 has a helical differential, and uses the same R200 carrier... will it fit into a s14 differential housing?

So.. I guess I really want you guys to fill in the blank spots in the last 3 types.
Thanks,
-Jeff

[dartman]

http://www.howstuffworks.com/differential2.htm

wow, that explains it pretty well :)

[AKADriver]

That link is a very good one.

I don't know why people keep throwing about the word "mechanical" - it's meaningless.

There's only three types - clutch, gear, viscous - for our cars. Lockers are beyond the scope of this forum unless someone plans on off-roading their 240SX.

Viscous, duh, we all know the VLSD.

Gear aka helical aka Torsen - stock in the S15, aftermarket from Quaife. Quaife supposedly preloads the gears a bit to overcome the freewheeling problem.

Clutch - pretty much everything else aftermarket, including the Phantom Grip, is this type.

Choose clutch for best performance, most noise, most maintenance. Because of the wide range of sources this can vary... a Z31 300ZX Turbo's stock clutch LSD will be silent but perform *worse* than a VLSD unless the clutches are modified.

Choose viscous 'cause it's cheap, works good enough for street use or non-drift, non-competition track use. A VLSD will eventually wear out (after a loooong time, depending on (ab)use) and can't be repaired.

Choose gear type 'cause it's good all around, least maintenance, won't wear out, and it's funny to say "Quaife"... dunno if you'd want it for drift but I don't drift so I have no clue. For drag racing they're not the best either. For street/"grip" at the track they're excellent.

Best for drag: clutch
best for street: viscous or gear
best for track: clutch or gear

[drift into a curb]

Still learning about LSDs, but the Kaaz is a clutch type.

[AceInHole]

Originally posted by AKADriver
Choose clutch for best performance, most noise, most maintenance. Because of the wide range of sources this can vary... a Z31 300ZX Turbo's stock clutch LSD will be silent but perform *worse* than a VLSD unless the clutches are modified.

Got a couple Q's....
1. Why would the Z31 LSD be any worse than a VLSD?
2. How exactly would you modify it? I'd imagine you could simply "load" the clutches by making it a bit tighter somehow?
3. I was under the impression that the z31 LSD would be better for track or autocross, having less pre-load than a VLSD (or so I thought).

[240 2NR]

Originally posted by AceInHole
Got a couple Q's....
1. Why would the Z31 LSD be any worse than a VLSD?[/B}

Apparently the stock nissan clutch breakaway torque is really low to kep it streetable. The number I've heard thrown around is ~30lb-ft, but this is with a datsun/sentra guy. I can't verify that it applies to the Z, but would assume a similar reasoning. Adding preload to the stocker could make it a better performer though I'm not sure how hard that is to do.

[B]2. How exactly would you modify it? I'd imagine you could simply "load" the clutches by making it a bit tighter somehow?

As I said, I'm not quite sure, though they claimed the easy swap generated an extra 100lb-ft of breakway torque, but by then it might as well be a welded diff.

3. I was under the impression that the z31 LSD would be better for track or autocross, having less pre-load than a VLSD (or so I thought).

Well the vlsd is the best streetable option. It's cheap and acts most like an open diff in normal situations (the only real downside is if you lift a wheel it acts exactly like an open diff sending all power to the wheel with no resistance, but how often do you do that?). A quaife is quite a marvel in my opinion since it can redirect torque and essentially prevent wheelspin before it happens (certainly before it can be percieved by the driver), while allowing for the streetablity of an open diff for tight manuvers like parrallel parking. If you've ever moved a welded diff car around a shop you'd see first hand whata pain it becomes. It also demands a different driving style. according to my frind who solo I's a 510 with a welded diff, it's very reluctant to turn unless under power. Clutch types seem the most popular drift setup, but for me are a trade off. Good grip sacrifices streetabilty and quiet operation and good street manners sacrifices grip. The benefit is the wheels are connected so until break away torque is reached, there's no wheelspin.

That's my $.02

[AceInHole]

Well.... I'm most likely going to attempt at getting a z31 diff to try out. If it doesn't work as well as I want I can just go to the VLSD later and machine my output shafts for it. There are a few cheap z31 diffs around here I think.... so I might as well give it a shot and see what I can do with it.

[DoctorT]

here it is... there is a lot of confusion here about different kinds of diffs do what with power. i read SCC cover to cover every month and remember seeing a very definitive guide to what the hell is going on inside the old rear end.

this is what i learned from reading tech stuff from all over the place.

VLSD:
a bunch of plates submerged in fluid. when wheel speed is the same all plates spin the same and it is acting like an open diff. when wheelspeed is different the alternating plates spin at different speeds, stirring up the juice causing it to expand and force the plates into spinning the same speed.

Clutch Type (KAAZ etc.):
also has a bunch of plates, but these plates actually touch one another. when twist is applied from the driveshaft the center of the diff. expands forcing the clutches together and making the wheels spin at the same speed.

so... the big deal about VLSD's versus CTLSD's is that VLSD's respond to difference in wheel speed and start working after one wheel is spinning faster than the other. CTLSD's respond to torque input and lock up based on how hard you push them (this is also adjustable by the arrangement of the plates).

for the CTLSD's the difference between 1-way and 1.5-way and 2-way is the angle that the vee-shaped groove is angled, causing different locking behaviors of the rear end based on throttle input and engine braking. 1-ways lock only in acceleration, 2-way's lock in acceeration and engine braking, and 1.5 ways lock in acceleration and lock half as much under engine braking

this is the article check it out the pics are awesome
(vee-shaped grooves rock)
http://www.sportcompactcarweb.com/projectcars/0308scc_proj350z/

as for HLSD's...
they use helically cut gears (explained in the article
better than i can) that respond to the torque by pushing against each other and sliding outwards because of the way the gear teeth are angled. this outward pressure creates the necessary rubbing to split power to both wheels (as long as there is enough resistance at each wheel, otherwise the gears wouldnt be able to push and slide out because one gear would be spinning freely).

this is the SCC article where i learned about Quaife diffs (awesome pics again).
http://www.sportcompactcarweb.com/projectcars/0309scc_projslivia/

in the nov 2003 issue they take their "project silvia" drifting with the HLSD, its not on the website yet because it is too new. drifting with an HLSD doesnt sound like a good idea to me...

-tim (w00t for my 2nd post)

[kandyflip445]

:squint: Thank you Doctor. If you were MY doctor I'd be dead months before you got to me....:rolleyes:






WELCOME TO THE BOARD!!!:D

[mrmephistopheles]

use the search button, fucking newbie!! :-D

actually Dorifto180sx did do a nice writeup on LSDs in FAQ..

[Jeff240sx]

Originally posted by mrmephistopheles
use the search button, fucking newbie!! :-D

actually Dorifto180sx did do a nice writeup on LSDs in FAQ..

Use the search button? Newbie? Ok Captain Can't Read... this post is nearly 9 months old! :hammer:
-Jeff

[Ka Drifter]

AceInHole is the Z31 turbo rear end the only one with lsd, I have a 85 non-turbo 5-speed junk car and I think it is a R200 housing and was wonder how you would go about hooking it up,would you take the gears out and replace the open unit or replace the whole housing
Thanks

[wingsnthangs]

http://importnut.net/nissan.htm