High lock diffs

[Jean]

Yeah 1600 is not not quite 650 lol

[matt]

$500? Are you modding ramp angles too?

The dog ear and clutch disc stack is 8.0 mm in thickness, right?

I am guessing you can free up some space by machining the endcap and grinding the shim on the opposite side... at least that's what makes sense to me.

Not modifying ramp angles at this point... We need a lot more R&D on that. I don't know exactly what it takes, Mike does it.

[Wanganstyle]

I hear you.

There isn't any other way to get slightly more lock, though, right, besides going to a 3 plate/disc combo?

Have you done any mods to the carrier to change the ramp angles?

you can go 4 plate - it gets to 60% 2 way high locking with stock ramps. Works well for track cars, although its not for NOOBS.

you can change angles to increase or decrease lock up, the factory does this (and many others)

its simple machine work, pick you desired effect (and angles) and have it done.

[Wanganstyle]

I can get OS Giken diffs if anyone is interested. We also build high lock-up stock BMW diffs with 2-4 clutches. Not for $850 though. It's $500 just in machine work to do a 4-clutch setup.

4 clutches can be done without ANY machine work. The DIY was written on e30 tech, I also posted a technical faq of doing one

if you guys are doing machine work WITH a 4 clutch setup, the costs def. can add up, many of the diff building guys are machining custom ramp angles for different characteristics.

4 clutch with stock center unit is NOT for noobs. You will shift lock like driving a KAAZ 2 way (I used to have a TOMEI *built by kaaz for tomei* in my drift car Ae86)

heres a guy doing stock 2 clutch replacement for reference:

http://forums.bimmerforums.com/forum/showthread.php?t=1115194

another picture tear down:

http://forums.bimmerforums.com/forum/showthread.php?t=894366

heres the original thread where I got the idea from; give credit where it is due!

this guy does a 4 clutch conversion with stock parts from a few diff;s

http://www.e30tech.com/forum/showthread.php?t=44131

another diff builders opinion on internal configuration:



street cars use a 40% lock is enough; three clutches.

For racing I use four clutches and change the pressure rings from 45º to 30º - this way you get 75% lock up rate.

To add four cluches you need to take off 4mm of material from the cover (use old type diff covers, they are thicker and have thinner bellevue washers)

-If you don't change the pressure ring to a 30º´s you get 60%. To get 90% you need 5 cluthces, but its too much"

from my experience, there are a few different styles of LSD internal, and it gets confusing. some need machining for 4 clutch, many don't. You can configure and adjust to the unit in your car.

my personal take on DIY of LSD rebuild/reconfig:


A. for LSD stock rebuild; easier than doing a head gasket. just remember how things came out, replace with stock items. You don't need a spare diff for this if you have a good workspace, if you have a lift removal of the diff from car is not even required!

A.5: for LSD install into place of open, paste, shims may be required. patience needed.

B. for LSD reconfig/re-gearing of diff:
** if you are hardcore DIY guy with alot of patience and the space to gather a few extra LSD's for parts, then go for it**

if you are building time attack car with lots of power then order a KAAZ :)

if your car is dedicated street and you just want LSD for rain, then get a stock unit or a Torsen :)

[Jean]

This sounds and looks fairly simple, but when you are upgrading from 2 clutches to 4, do you just stack them up or what exactly do you have to do in terms of installation order?

[Wanganstyle]

Local guy gave me this to tear down

188mm 4.27+1,000rwhp and MT's

[Jean]

LOL nice

[Wanganstyle]

Did a high 9 pass then died on 1-2 shift second pass. Hahahaha

If u look the clutch plates alternate w disc. If you reference the diagram of an OS GIKEN unit or cusco, you will see what I mean :)

[Jean]

Ok, I think I want to give this a shot. Where can I get these clutch kits from, if these are oem parts can I just get them through a local dealer?

PN # ?

[Wanganstyle]

ok, i think i want to give this a shot. Where can i get these clutch kits from, if these are oem parts can i just get them through a local dealer?

Pn # ?

33141210626

[u3b3rg33k]

Since I love jumping on the torsen bandwagon I figured I'd chime in late here.

I swapped out an OE LSD for a Z3 torsen, and I find that the torsen does a better job. Granted the former had 170k on it, but I'd rather change oil than rebuilding a diff.

I do use the parking brake trick in the winter at times. Try that with an LSD. It does nothing.

[FredK]

33141210626

This is the part number for the clutch friction disc.

If you wanted to add one or more discs, I believe you'd need to source thinner dog ear plates (the plates that the discs mate against).

I'm still not sure how you can get 75% lock / 4 plates with stock parts. Can you describe how that's done?

I just serviced the pinion bearing on my diff and inspected the clutch discs and steels which looked ok--if the diff is quiet I'll probably fool around with building a 3 disc setup.

Granted the former had 170k on it, but I'd rather change oil than rebuilding a diff.

Honestly restacking the clutch discs inside the LSD is not that difficult. It might take a few hours the first time but the second time it'd probably take half that. Changing the pinion gear bearings is slightly more difficult.

[u3b3rg33k]

The real reason i pulled mine was that it was getting noisy. I'm pretty sure it needs a full rebuild.

[Jean]

Thank you.


I would like a confirmation on the necessary parts to replace the original 2 clutch disks with 4 to get this done .

I promise to take lots of pictures for others as well :)

This is the part number for the clutch friction disc.

If you wanted to add one or more discs, I believe you'd need to source thinner dog ear plates (the plates that the discs mate against).

I'm still not sure how you can get 75% lock / 4 plates with stock parts. Can you describe how that's done?

I just serviced the pinion bearing on my diff and inspected the clutch discs and steels which looked ok--if the diff is quiet I'll probably fool around with building a 3 disc setup.


Honestly restacking the clutch discs inside the LSD is not that difficult. It might take a few hours the first time but the second time it'd probably take half that. Changing the pinion gear bearings is slightly more difficult.

[Wanganstyle]

This is the part number for the clutch friction disc.

If you wanted to add one or more discs, I believe you'd need to source thinner dog ear plates (the plates that the discs mate against).

I'm still not sure how you can get 75% lock / 4 plates with stock parts. Can you describe how that's done?

I just serviced the pinion bearing on my diff and inspected the clutch discs and steels which looked ok--if the diff is quiet I'll probably fool around with building a 3 disc setup.


Honestly restacking the clutch discs inside the LSD is not that difficult. It might take a few hours the first time but the second time it'd probably take half that. Changing the pinion gear bearings is slightly more difficult.

You are totally correct. if the nut behind the wheel can trust self to build engine, then can build a diff. If the nut behind wheel can't do a head gasket confidently, then diff work should be left to a professional.


there are only a few OEM dog ear plate thicknesses, if you tear down the diff and measure everything, you will be able to figure it out. factory PN's for the dog ears have them in a range between 1.8-2.1mm

Different year diff builds have slightly different thickness spacers inside - having a few is nice. Early cases are small clearance hole in side, later are big cavity. very early is also slightly different spacer stack internally.


OEM 4 clutch + stock ramp angles is 60% lockup. Modified ramp angle can get you to 75%

you can also preload or increase pressure with spacers/springs/bellvue, but IMO its kind of weaksauce overclocking.