High lock diffs

[FRODADDY]

Hi there,

my E30 diff is toast and now I am curious what to choose.
My car is mainly a track car, I wish have a little bit higher locking capability.
So either I'd use 2 2,1mm Porsche clutches with thicker 2,1mm Porsche dog ears or I go the way of a three clutch setup.
That would mean an extra 0,4mm of the whole package, is that too much?
I dont want to have too much preload either.

What suits me better?

[shiboujin]

If you got the cash.

[agent]

reasons everyone should open their lsd.

Or buy one that's been professionally rebuilt.

[shiboujin]

reasons everyone should open their lsd.

[LivingLegend06]

Not sure, The user I got it from estimated mileage at 150k but said he had a low level of confidence. I believe he got it from another user on here who found it in a junkyard car so who know how many miles are really on it. I have put maybe 8,000 miles on it since then.

[shiboujin]

how many miles on that diff?

[LivingLegend06]

Saturday I swapped in an open diff I had so that I could begin the rebuild process on my worn out LSD.

My plan is to build a 3 clutch unit using OEM clutches and new 2.0mm dogears
I am planning on ordering:
3 X 33141210626 (clutches)
3 X 33141203796 (2.0 mm dogears)

I tore my diff apart yesterday to assess the current condition, I was hoping to be able to reuse my dogear plates to save a little money but after seeing them I think its best to just replace them.



Hmm, one of the clutches appears different from the other...


The center carriers have some clutch material transfer as well, I do not really want to have to take these parts to a machine shop but I may have to.






The nasty dogear and nasty center carrier were from the side that still had teeth (the side that was still doing a little work). The oil that came out wasn't too metallic but after handling these parts my hands turned silver from all the little metallic particles.

Depending on how much material has to get removed from the center section I may end up going with 2.1mm plates to make up the difference in lost material thickness.
The gears and bearings all look like new so I wont be replacing them, the spider gears have a few little marks where they make contact but I cant feel any edges so they should be fine to go back in.
I'm sure that a rebuild unit is going to make a huge difference over my extremly worn unit with only 1 working clutch. Hopefully I can have it back together in time for the rainy season :)

[Wanganstyle]

I have a dead LSD that I'm either going to rebuild or replace. I'm considering doing a 3 clutch build with no machine work, it seems that for less than the cost of a good used factory units (under $300) I can build a better than stock LSD.

I'm having trouble choosing which dogears to use:
-Reuse existing, this will likely result in the least preload as they spacers will be worn and less than 2.0mm thick.
-New stock 2.0mm, this should give me approximately stock preload. Cost would be more than reusing existing dogears.
-Porsche 2.1mm, this would maximize preload. Cost would be about the same as new stock dogears but I would get more lock. My concern here is that there will be more forces on the clutches during everday driving that will wear them our faster.

I dont get a lot of snow where I live and even if I were driving in the snow I'm not all that worried about getting lockup on low traction surfaces which seems to be the only advantage of the additional preload. If my thinking is correct once you overcome the preload the amount of lockup on would be the same between the different builds regardless of how much preload you started with(does anybody want to contradict this?). If thats true than I see no reason to put the extra stress on the diff by adding 2.1mm dogears for extra preload.

Now that this thread is getting old can anyone comment on the life of a rebuilt high preload diff? The diff is a 3.73 going in my M50 powered daily driver and will see some track use but not nearly as much as some of you guys.

If I build this LSD unit with my existing 3.73lsd would it only be useable with 3.73 gearing or would it be possible to go to taller gearing in the future If I decide to go to a ZF trans or S5X power?

Rebuilding dead stock units with brand new wear parts is like changing out dead brake rotors and pads- the little lsd discs do the same basic function as brake pads and rotors.

Gear ratios from 3.15-4.88 are all directly compatible: plug and play.

Extra preload would be good if you are going to add weight into the car: ie a competition stereo with lots of tv's etc.

Bmw uses higher preload springs in e32 735il cars (3.45mm Belleville springs vs e30 2.45mm springs.
Additional preload helps the heavier il model climb up steep driveways and lock up quicker for rainy days-

Preload increase = static stationary lockup increase in breakaway torque = harder to turn from starting = requires more force in (load/weight/torque/use of stored or potential energy). A LSD with lots of static lockup on a light underpowered car will handle like a welded diff- cars with welded diffs (spools) are great for drifting and also road course use (strictly racing not street car use)

For motorsports bmw factory lsd unit has no preload springs- yes the Belleville spring is deleted and an asymmetrical center ramp section and 4x clutches/steels with 45/55 effective angle is used for a 1.5 way action-deccel lockup is decreased proportionally and acceleration lockup is increased from 4x disc setup vs 2x.

The stock lsd
+
Extra preload
= more understeer:

With additional clutches the lockup on deceleration will also increase- lsd lockup makes you go straight as its limiting the work that the differential usually does (differentials let 2 different wheels get power from one driveshaft).

You could replace the clutch discs with thick 2.4mm porsche and custom grind the steels and surface the center ramp plates to make up for distance.

Or you could go to non organic metal matrix discs and steels (I use proprietary units for higher stress and lockup without more preload or discs than stock)

Sent from my GT-N7100 using Tapatalk 2

[LivingLegend06]

I have a dead LSD that I'm either going to rebuild or replace. I'm considering doing a 3 clutch build with no machine work, it seems that for less than the cost of a good used factory units (under $300) I can build a better than stock LSD.

I'm having trouble choosing which dogears to use:
-Reuse existing, this will likely result in the least preload as they spacers will be worn and less than 2.0mm thick.
-New stock 2.0mm, this should give me approximately stock preload. Cost would be more than reusing existing dogears.
-Porsche 2.1mm, this would maximize preload. Cost would be about the same as new stock dogears but I would get more lock. My concern here is that there will be more forces on the clutches during everday driving that will wear them our faster.

I dont get a lot of snow where I live and even if I were driving in the snow I'm not all that worried about getting lockup on low traction surfaces which seems to be the only advantage of the additional preload. If my thinking is correct once you overcome the preload the amount of lockup on would be the same between the different builds regardless of how much preload you started with(does anybody want to contradict this?). If thats true than I see no reason to put the extra stress on the diff by adding 2.1mm dogears for extra preload.

Now that this thread is getting old can anyone comment on the life of a rebuilt high preload diff? The diff is a 3.73 going in my M50 powered daily driver and will see some track use but not nearly as much as some of you guys.

If I build this LSD unit with my existing 3.73lsd would it only be useable with 3.73 gearing or would it be possible to go to taller gearing in the future If I decide to go to a ZF trans or S5X power?

[yeaseth]

Im rebuilding my 3.91lsd tomoro with the 2.1mm dog ears and bimmerworld clutches, Hope it all works!

[u3b3rg33k]

What car do you have/what engine? Even with m10 that I had in there before I could easily get them to spin in 1st?

Looks like I never answered your question, but since the thread ain't dead, I have a z3 torsen with an M20 in front of it. Good rain rubber, too.

[TobyB]

If you want a lot more lockup, why not just run a welded diff?

Raced the 2002 that way for most of a decade- it works. You can set the suspension
up to compensate for some of the quirks, and the others, well, they become tools.
It doesn't beat up halfshafts or driveshafts particularly, and that's with small case parts.

That said, it's not for the street- I did some emergency break- in and testing by putting
one into the street car, and it was miserable. Period.

t

[Jean]

What car do you have/what engine? Even with m10 that I had in there before I could easily get them to spin in 1st?

[u3b3rg33k]

So, too much lock in the wet?

I was able to punch it in 1st through an intersection in the rain the other day, and the ties didn't break loose - I don't know how that's physically possible.

[Jean]

Wanted to update this thread since I had a chance to drive it in rain. I am using 225/45 (or 50) Kumho AST tires on 15x8 wheels, so not exactly skinny or anything.

A little scary at first, VERY tail happy if you are aggressive with throttle....2nd gear spins all the way to redline w/o any traction I can just keep it spinning into 3rd half way. Giving it a little bit of gas in mid corner will cause the rear to slide but quick correction/letting off and it gets right back in shape.

Now, while accelerating slowly w/o any wheel spin in 2nd gear, giving it more gas whips the rear as well

But yeah, no noises or anything, still grips like mad when dry!