legacycentral bbs

EDIT 10/13/2016:

fateo66 wrote:Ok gents, here are all the OEM subaru LSDs that you will find in a R160

Starting from the left you have a standard open diff, if you look closely you will see the pinion hears inside all chewed up. This is what happens when you blow your rear diff.

Second LSD in is a viscous unit from either an RS or wrx. they look very similar to an open diff however the plate which you mount the ring gear to splits in half which is where the viscous fluid and disks reside. IMO what makes this diff so crappy is the fact that it only has two pinion gears internally to distribute the load, just like the open unit.

Third LSD in is from a 91 legacy SS but also came from some JDM cars and the SVX (however the svx uses a different spline count on the axles and is completely incompatible with a impreaza as far as I can figure out) These are a viscus unit too however they have 4 pinon gears which makes them much stronger. This and only this diff uses the axle with two sets of splines.

The fourth LSD in the picture is a clutch pack unit or MLSD. This diff came as an option in some 80's subarus along with some JDM cars. Note the squared off top to the LSD casing, also this unit uses bolt in axle stubs.

From http://www.rs25.com/forums/f8/3119939-post17.html

Here's a fun picture:


And an even better thread:
http://www.rs25.com/forums/f8/t205522-s ... tials.html

mike-tracy wrote:I don't know, but if you find a 4.44 MLSD (not CLSD) I'd be interested

Your comment confuses me on what I thought those acronyms meant. I always though people were referring to clutch-type LSD's anytime they specified "mechanical", but your statement implies otherwise.

Yeah, late model GC's had a torsen type diffie, early had clsd. Another bonus of the late GC diff's, no unequal length axles needed!

my best suggestion is look on ebay.co.uk and ask them if they'll ship to the usa

To clarify what I'm saying: Subaru made 3 main kinds of "LSD" rear diffs in the 90s - VLSD, CLSD, and MLSD. Of the 3, the CLSD is the most effective, and can even function as the opposite wheel has no traction. The MLSD needs the opposite wheel to have traction or it acts like an open.

The factory MLSD diffs do not need special axles. The factory GC8 CLSD diffs DO need one longer and one standard axle. Running 2 standard axles do not activate the LSD. Blackbart's setup is presumably from a GL10/RX/the like, and it came with 2 normal length axle stubs, so no special axles are required.

Okay, so it sounds like what you're calling a mechanical LSD is a helical-type (or gear-type) everywhere else. I never knew or heard of Subaru offering helical rear LSDs, even what they called Torsen rear LSDs were still clutch-type from my understanding (Torsen in that regard being a brand name rather than a specific type of LSD). I've only known the front LSDs in some of the STI transmissions to be helical.

The only helical rear diff I've seen for Subaru have been aftermarket from PPG, Quafie, OBX, etc.

Check out a ver 5-6 sti sometime, you'll see what i'm talking about. I'm refering to r160 diffs, though the 4.44 R180 is a mechanical torsen type lsd as well.

Have any links to pics with the covers removed? I've looked into LSD types quite a bit and never saw mention of a helical factory rear diff. I've seen mention of mechanical, but that term is definitely used to identify both clutch and helical LSDs depending on who says it and where.

Ill look for some links with pics. When you say you haven't heard of a Subaru with a Torsen type diff, what would you consider the one in a GD STI's r180?

Im gonna split this topic up when im home, so poor dankberries can get the diff he needs

lol, sorry about the hijack. I'm not trying to be a dick or anything, but there's some hazy info floating around and I want to know what's actually out there. I'll wait until after the split to continue.

OK, this never happens...but... when I said rear helical, I must have been referring to rear Suretrac lsd. Can't find a thing about a factory R160 with torsen-type rear.

I actually owned one in 4.11FD a couple cars ago, and sadly sold it. It was JDM, either from a late GC STI or early GD (Wrx presumably), and took standard male:male rear axles.

In my research, I found Subaru used a few different rear diff types in the GC era:
- Screw Refuse type (VLSD) (not just what the Mrs does )
- Sure track mounted LSD
- Mechanical cable type 2way LSD

I'm not sure what the last one means exactly, but it was fitted to cars with the 5mt DCCD. All of which had 4.44FD R180's except for that elusive DCCD box with the r160 & 3.9FD.

I've seen the mention of mechanical cable-type 2way. I've always chalked that up to funky Japanese translation. No idea what it means either though.

All the pics inside of an STI's pumpkin (including a couple GCs, but not sure on the years) I've seen are clutch-type, o at least appear to be so. And I've seen lots of mention of clutch type diff's from the JDM cars. But nailing down that "other" type, that gets alternatively called mechanical and different names, seems to be elusive right now.

I feel like just a simple pic of the carrier with the worm gears would clear it right up... Tons of pics of clutch packs. Are these other diff's just that uncommon?

Hey man, you are in the Jay Dee Emm Motherland, I was hoping you could provide some answers, lol!

I'd love to! But my work schedule is super crazy here and I haven't had a chance to really get myself into the car scene at all. Hopefully it'll slow down this summer and I can actually make some gear head friends and scope out some junkyards.

Dammit. I've been searching on and off all day, and all I've been able to do is clarify that people on the internet love to cite facts with no sources and contradict each other.

And yeah, that damn word "mechanical", there's definitely a lack of consensus on whether it means clutch-type or helical-type.

But as far as I can tell helical rear diff's do exist from Subaru, just absolutely zero agreement on when and on what.

Seems like I always thought they were all clutch type due to the serious lack of clear, cohesive terminology

Its my understanding that in some VERY RARE 1993-1994 wrx Sti models Subaru made a non- clutch type LSD4.11.

Through all my research I thought this was deemed the best functioning diff of the three supposed types.

Mike, you stated that the CLSD is capable of powering both wheels even with one off ground. You believed this to be the best of the three.
Hopefully we can get the diff mysterys figured out. I want to know every available r160 LSD Subaru made.

For what its worth NASIOC diff FAQ:
http://forums.nasioc.com/forums/showthr ... ?t=1126026

Clutch type has its disadvantages too. The clutches wear out, and its a noisy diff to live with. I have one and thats why i want to try something different.

It also depends on the setup of the diff. You can make a clutched diff seem pretty mild and not as noisy by changing the preload and ramp angles. I put a 1-way front in a street car years ago with setup advice from cusco usa and am told it has been pretty much silent and seamless.

Personally I think a clutch diff is preferable on a car like a subaru because they tend to unweight/pick up wheels, which makes a helical diff useless.

James614 wrote:Dammit. I've been searching on and off all day, and all I've been able to do is clarify that people on the internet love to cite facts with no sources and contradict each other.

And yeah, that damn word "mechanical", there's definitely a lack of consensus on whether it means clutch-type or helical-type.

But as far as I can tell helical rear diff's do exist from Subaru, just absolutely zero agreement on when and on what.

Seems like I always thought they were all clutch type due to the serious lack of clear, cohesive terminology

I generally refer to helical/torsen type diffs as "mechanical," and then clutch type diffs as "clutch" diffs. The subaru trans chart rallispec made should list the type of differential that goes with every model/year/trans.

http://forums.nasioc.com/forums/showthr ... ?t=2173258

Helical is a generic term while torsen and suretrac are brand names (also they have slightly different mechanisms but work pretty much the same way). Then plated means a clutch diff.

Okay, so the Suretrac and Torsen diff's are both helical? If that's the case then its really not that complicated given Rallispec's chart.

The issue is that between the serious lack of consistency with referring to only the helical diff's as mechanical, (I've found threads comparing "mechanical vs helical" for example) and the fact that as far as I can tell, Subaru's helical rear diff's do not have exposed worm gears and don't look that special to the untrained eye, it was simply never apparent in the past that there's more than one type of non-sucky (not viscous) LSD that was used over the years. The brand names Suretrac and Torsen never meant much, because I've heard numerous people go out of their way to mention that those are brand names and don't necessarily mean they are a certain type of LSD. I've even seen a couple places claim the Torsen was a clutch type that could be rebuilt with tighter clutch packs. Those people were probably talking about a non-Torsen diff, but just used the word because they know Torsen=LSD.

This actually potentially saved me a rather expensive and pain-in-arse mistake, as one of the Torsen or Suretrac diff's was on my list of potential sources of an inexpensive clutch-type LSD. I would have been really butt-hurt if it acted open off-road. I THOUGHT I had Subaru diff's rather well researched, lol. That's the internet for you.

The extra confusing thing is that it mentions helical for the front diff's. Are those just Subaru's own design? Are Suretrac and Torsen notably different enough to warrant differentiation from just an in-house helical diff?

The Datsun 510 guys are known to use Subaru LSDs as upgrades for their cars, since 510s also came with R160 differentials.

I found this thread in some of my research, and it's good for identifying certain types of Subaru LSDs:

http://www.the510realm.com/viewtopic.php?f=1&t=11471

James614 wrote:The extra confusing thing is that it mentions helical for the front diff's. Are those just Subaru's own design? Are Suretrac and Torsen notably different enough to warrant differentiation from just an in-house helical diff?

Yes. The end result is similar, but suretrac is made by AP and Torsen is a trademark so they can't just call them all "helical diffs." Also the suretrac mechanism is slightly different.

edit: here's some info about the Subaru helical diff from rallispec:
http://www.rallispec.com/dif_gls_rst1903_t.html

thought I would add that my V.4 R180 (not R160) clutch pack LSD has STi regular inner-cv joints/studs. I bought mine new from the dealer, they are for an early 2004 STi. The only difference between the later years is number of balls in the DOJ. Early has 6 balls, while the later has 8. My build thread shows my converted axles, and the rebuild of the diff.

I thought I would add to the tread since axle stud lengths came up.