LSD complications (within S-chassis)

[adey]

I know this has been discussed before (I probably saw it on FA, the search on zilvia came up with nothing useful), but I think it would help to have an easier-to-understand and more recent version of it up here, especially since there have been so many LSD (limited slip differential) topics recently.
With the growing popularity of drifting and the growing sales of LSD (new and used) there still seems to be a mist hovering around the somewhat complicated topic of LSDs and which ones will fit in our cars.

I will share my assumptions (I don't know any of this for sure) about the usability of different S-chassis (read: NOT J30 or Z32 differential parts) between JDM and USDM S13 LSDs, side shafts ('output shafts' or 'axles'), flanges (flange), pumpkins and LSD, VLSD, and open differential units.
In other words, I DO NOT KNOW WHAT I'M TALKING ABOUT, AND SEEK YOUR CORRECTION OF MY MISINFORMATION. (so please, don't take any of what I say too seriously.)

end introduction
================
begin (mis)information

Glossary:
- LSD: (actual "hat" shaped thing that goes INSIDE the outer shell; the "guts" of a pumpkin, if you may.)
- Pumpkin: Outer "shell" of the differential. AKA Differential Case or Housing.
- Output Shaft = flange(s), output flanges; the piece that sticks out of the differential. 2 flavors: 3 tab, 6 hole USDM style, and the 5-tab 5-bolt JDM style.
- Axle: the long piece that connects to the hubs via splines that are often rusted together. This piece bolts to the output shafts of the pumpkin. (AKA "Half shafts"?)

Currently in the market (well, sort of) for a 2-way clutch type (aka mechanical?) LSD, I have come across a number of problems surrounding which axles (aka half shaft?) that I will need and what flanges will mate up with what axles.

For example: I'm currently looking at a 2-way LSD that includes the whole Subframe assembly; that is, all arms, hubs, rotors, calipers, shafts (aka axles), and the LSD (pumpkin) itself.
With this, it is "easy" to do, because I have everything I need:
- the JDM VLSD pumpkin with a 2-way LSD in it -- this has the 5-bolt star shaped flanges sticking out,
- two JDM 5-bolt star-shaped axles.
I'll go over why this is good further down the post.

What's most sought after stateside is not so much an actual LSD so much as these 5-star axles. The S13 USDM VLSDs (apparently quite hard to find used) came with 6-bolt (triangle shape) side flanges, and will bolt up to open differential axles which should also be 6-bolt triangle patterned.
(Unfortunately, I'm not sure of what the USDM S14 axle bolt patterns are like {for either open or vlsd}... so I'll let someone else touch on that.)

However, the JDM VLSDs (or VLSD pumpkins with after market LSD) which seem to be more abundant, came with 5-bolt star shaped patterns... which do not bolt up to either S13 open or VLSD axles. (MAY bolt up to S14 axles, although I don't think the rear pumpkin cover will bolt up to USDM S14 subframe)

So. You have an Open diff and what a 2-way LSD. What do you do?

(S13)
- You need to find an S13 that had a VLSD, grab the pumpkin, swap out the internals of that (with your LSD), replace the RIGHT (I think-- whichever side is LONGER) flange with another LEFT (shorter) flange from another VLSD and replace your open diff pumpkin with this new frankenstein-of-a VLSD (now with 2-way LSD inside) pumpkin into your S13. (about on par with third method outlined below in terms of difficulty) The pumpkin with modified output flanges will mate up to your stock USDM axles.

- OR: find a JDM pumpkin with 5 bolt flanges, get JDM 5-bolt axles to go with it. Take out your current axles (can be a SERIOUS pain in arse if your splines have rusted together), replace your axles and pumpkin with JDM units. (Depending on how big of a headache pulling your axles give you, this could be the hardest way to do it)

- OR: {probably easiest to do?} With JDM LSD & pumpkin, open up the pumpkin and replace both side flanges with USDM VLSD left side (short) 6-bolt flanges. (that's right, you need two short ones-- US VLSD flanges were different lengths.) Then bolt this up to your stock 6-bolt, 3-tabbed axles. (have the flanges swapped out by a shop or at least someone who's done it before, it's important that all internals are kept in good alignment/spacing.)

There are other ways to get an LSD into your car, but I think the 3 up there are pretty much the most popular and/or convenient ways to do it. If you can grasp the concepts of which cars have 6-bolt tri-tabbed (triangular, if you may) flanges and which have 5-bolt 5-tabbed star shaped flanges, it should make a lot more sense.

end of my babble.
=================

Umm... that said, can anyone confirm for me that it is indeed two of the SHORTER (LEFT) VLSD flanges that are needed to work with an aftermarket LSD, and that will bolt up with stock axles?

[Dousan_PG]

some more ot add


kouki 180sx were 3 flange on the LSD side shafts. how do i know?

www.nismo.co.jp

my SSS said so, ordered that model
nissan is lame and kept changing stuff.

my LSD i have on my currently was 3 flange too, straight from japan.

j30 is 5 flange. if someone gets a LSD/vlsd just get j30 side shaft deals (one that goes to wheel)



where's drift freaq?????

fyi: in japan, VLSD are junk. they want to get rid of that stuff at the junkyard. i agree. lol. once you go true LSD you'll never go back
glad to hear from you yesterday man! you wont regret it!

[RBS14]

95' and up J30's are 3x2 output shaft pattern, bolts right into a S chassis.

[AKADriver]

Blah 3.9 ratio though, and the bushings on the front attachment points need to be supported by washers in an S13... Considering the VLSD isn't all that great to begin with, the J30 stuff just has too many disadvantages for me to consider or recommend.

BUT the J30 isn't all bad.

'95-earlier J30 axles are 5-star and will work with a JDM 5-star output shaft S13 diff.

[drift freaq]

where's drift freaq?????

right here.
Damn adey, I thought I was the only one, who could be long winded , hahahhaha J/K.
Lets get right to the point. JDM VLSD's for the most part are 5 bolt or star flanges . This is problem is easily taken care of , you use pre 95 J30 axles, in fact this issue is covered in my VLSD faq. Its no different with the JDM diff as it is with the pre 95 J30 diff.
Ok , next up bolting a later model differential S14 VLSD be it JDM or USDM can be done. Simple things to remember. Change your back cover from your stock S13 differential because it is 4 bolt vs 2 bolt of most JDM ones. The other thing is, you need to get the eyelet bushings as well as the bolts and washers that come with the S14 VLSD. Again, these are the same issues you would have to deal with putting in a 300 x VLSD.
As far as the output flanges for USDM S14's go they are 6 bolt just like S13 USDM.
(To add one more detail to this confusion there were JDM VLSD's both S13 and S14 that came with 6 bolt. It all depends on the year.
You have to look at it from an assembly line basis. certain parts were availible at certain times from the forge so thats what was used . If they ran out they grabbed the other ones.)
Ya I know you did not want to hear that adey. But its the facts.

Got a KAA ( damn dead key )?? then you do need output flanges. Buying VLSD or LSD output flanges from Nissan new is a expensive ordeal . Try $250-270 and back ordered to the moon. You are better off pulling out your stock diff flanges and grinding down the right side one the two will then fit. doubt this? Mattback on FA did it .
Or like adey did say you can pull the output flanges out of a USM VLSD. the choices are yours.
Also for those of you in the market for a KAA remember that you also need to install your ring and pinion. It does not come with one installed.

AKA driver, putting a 3.92 J30 diff in a turbo car can actually be an advantage due to the fact that it keeps you in your gears roughly 4% longer time thereby engaging your boost that much longer.
Yes the J30 3.92 diff is roughly 4% different in gear ratios . Unless your drag racing and you are worried about a 1/4 of a second its no big deal.
there it is guys most if not all of this stuff is indeed covered in one way or another in my faq , but this does clarify a few things adey was wondering about.