High lock diffs

[lolcantturn]

I don't have any use or need to rebuild or do anything with my LSD



But this thread is fucking awesome. I got so into it haha.

[CabbE30]

So much good info in here.
Was just going to start my search for a lsd.

[JakeP]

Has anyone actually tried the Viscous Diffs out of an IX and wore one out? I don't think it's possible to do based on the design.

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

[Wanganstyle]

Drifting is so awesome. STICKY IT NOW.

I love drifting too!!!

[Jean]

Thanks!

[u3b3rg33k]

On that note:



(T-2 type)

(T-1 type)

[shiboujin]

I'll leave these here:

Explaining lsds

http://e30performance.info/viewtopic.php?f=22&t=1311&hilit=lsd

Adding lock

http://e30performance.info/viewtopic.php?f=22&t=939&hilit=lsd+rebuild

[Wanganstyle]

Thanks man!

Spoke with a local diff place today recommended to me by a local scca chapter. I took a neutral approach with my questions to not show any bias either way, it seems that his thoughts are to use even number of clutches in the build vs odd.

How valid is this, I would like more discussion on this from those with experience.

Oem compromise design of the clutch diff wears one side of internals more than the other. Doubling clutches on one side only might shock load one spider side more than the other- heat stress is an issue as well, as severe heat will cook the organic material- I have seen glazed discs and tons of uneven wear is common.

At least the diff shop guy is telling you from experience.

[Ian Bowers]

This thread is so awesome. STICKY IT NOW.

[Jean]

Thanks man!

Spoke with a local diff place today recommended to me by a local scca chapter. I took a neutral approach with my questions to not show any bias either way, it seems that his thoughts are to use even number of clutches in the build vs odd.

How valid is this, I would like more discussion on this from those with experience.

[Wanganstyle]

Ok, here is another question for those with experience.

How do you determine how much lock is going to be enough or how much is too much?

Maybe I need to list some car stats? Car is fairly light (2500lbs, tires currently are 225/50 15 v710 30 treadwear, coilover suspension, camber plates no rear bar, and m30b35 swap). Next season m30 is going to be replaced with a 4.0 or 4.4l v8 so another 80 or so hptq over b35 and tires will also be wider most likely 275/35/15 size. Rear end is 3.64 and I am considering going to 3.46 or even 3.25. Issue is currently spinning the inside rear under acceleration out of the corners, and these aren't hairpins some are fairly good size / wide turns. If the surface is dusty or dirty there is even more problems putting it down when the car is already pointing straight.

Also, would doing a 3 clutch vs 4 clutch result in one side / wheel to be able to put more power down vs the other? My concern is "uneven wear or load balance" if that is the case when you go with odd number of clutches?

Now that I have a 2 month break before next autocross rounds, I have the time to get this done but need to understand this more so I can order the right parts.

Thanks!

Technically speaking, if the diff center is locked up, both wheels should be locked up as the output shafts are splined to the center spider gears.
if you have a destroyed or dying clutch, then perhaps it could have un-even torque to the rear wheels - most extreme would become an open diff- I have had this happen to my own diff before.

as far as uneven wear goes the design of the oem 2 clutch unit wears one clutch disc more than the other. 3 disc is popular because of the cost; also that design constraints of the unit make 3 clutch suit street cars better. Cheaper+larger audience = good for business!!

if a Viscous or Garbage addition (phantom grip) diff was setup correctly, it could provide enough lock for any application. Problem is this rarely happens; thus the aftermarket LSD industry.

BMW uses a very OEM style diff setup; the design of the diff tends to wear the clutch plates unevenly and with a bit of glazing as well, as the side springs add tension BUT un-even distribution of forces - you will see the wear when you take yours apart, it looks similar in every stock diff- un-even wear is shown on dog plates, clutches, springs. Using a heavy duty spring puts more tension on the plates so they lock harder and SAVES MONEY WITH LESS PLATES - But handles better.


Open diff handles the best if the setup allows it. usually with FR cars this is not the case- BUT some FR's handle better with open diffs.


ZF188mm is not an aftermarket KAAZ/cusco/os-giken designed for lap time, drifting. The "custom center ramp" business was designed around playing games with OEM configuation commuter LSD because of the inherent downsides to adding more lock to this style of center section.

if stressed to extreme (motorsports use with slicks), the splines of the clutch disc can go from 27 splines to = 0. I have destroyed one prior drifting, and the disc was fused to the center section...... was FUN times smoking tires!!!



You seem to be having similar problems as bolt on footwork Nissan 350z's. Nissan OEM's a viscous LSD that overheats and becomes = open diff with sticky tires. Z can run 19's all day long and huge slicks with hardcore suspension - kills the viscous LSD. Viscous diff is great for parking, malls and picking up girls, not for drifting or lap time.

if you want a feel like a KAAZ or Cusco (japanese competition diff) you would want a 4 clutch unit with 60% locking or variable center section with at least that kind of locking- in comparison, a Kaaz or Cusco has much more aggressive locking avail in stock configuration and handles better than a OEM bmw diff modified with 4 clutches because they dont rely on side spring like the bmw for pre-load. Side spring just keeps things tight, many very high quality friction discs (often carbon) and higher stress design






OS giken gets even fancier and has a sprung center cartridge; this is a 911 unit IIRC



Porsche uses various ZF LSD units for many cars OEM (as ZF was told by Dr. Porsche to "CREATE LSD")
some of them do not use bellvue washers, have clutch on clutch lesbian action in the stack, have no spring (or minimal tension), etc etc.

you can really open this up to massive configuration if you want to open up the history book. DNA, DNA, DNA....... I may be doing one in very un-conventional fashion for my own car Japanese aftermarket style pretty soon :)

[Jean]

Ok, here is another question for those with experience.

How do you determine how much lock is going to be enough or how much is too much?

Maybe I need to list some car stats? Car is fairly light (2500lbs, tires currently are 225/50 15 v710 30 treadwear, coilover suspension, camber plates no rear bar, and m30b35 swap). Next season m30 is going to be replaced with a 4.0 or 4.4l v8 so another 80 or so hptq over b35 and tires will also be wider most likely 275/35/15 size. Rear end is 3.64 and I am considering going to 3.46 or even 3.25. Issue is currently spinning the inside rear under acceleration out of the corners, and these aren't hairpins some are fairly good size / wide turns. If the surface is dusty or dirty there is even more problems putting it down when the car is already pointing straight.

Also, would doing a 3 clutch vs 4 clutch result in one side / wheel to be able to put more power down vs the other? My concern is "uneven wear or load balance" if that is the case when you go with odd number of clutches?

Now that I have a 2 month break before next autocross rounds, I have the time to get this done but need to understand this more so I can order the right parts.

Thanks!

[Jean]

Wanganstyle - PM sent buddy.

[Wanganstyle]

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.

I love the torsen in my E30 :)

[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.