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Old 11-01-2012, 01:47 PM   #1
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Default Check my LSD theory

So, for those of you that don't know, here's the general order of my RX-7 clutch-type LSD. For this example the "()" are the conical spring washers that put tension on the clutch packs.

axle-(-clutch pack-spider gears-clutch pack-)-axle.

So a mini clutch pack for each axle.

In order to increase the torque at which the axles break free, you can put a shim behind the conical washer to increase tension.

I've tried two coke can shims and it only gave me 10 extra foot pounds. Coke cans are apparently .005" thick. I made two .015" shims out of my old ECU (recycle!) and the torque was well over 110 ft/lbs. I took one shim out, so now there's only one .015" shim under one conical spring. And I'm at 110 ft/lbs, right where I want it to be.

My question:
Will this cause one side to break away easier than the others, or since it's just a spacer, is the extra tension spread over to the other side as well?

Yes, I could make two .0075" shims, but I don't have that kind of material laying around.

Here's my baller torque sensing setup:



Thanks y'all.
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Old 11-01-2012, 01:51 PM   #2
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Unless the entire center section floats between the two mounting points, it will cause one side to have more tension than the other. If it does float, it will self center and equalize.
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Old 11-01-2012, 10:59 PM   #3
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The limitedslippedness is the same no matter how the clutch is distributed between the two sides, but I don't want to think about stresses the spider gears see if things don't float to balance the torques.
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Old 11-02-2012, 09:33 AM   #4
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Yeah, it's all floating. rleete's post really made it click in my head, it doesn't matter. So I assembled the diff in it's 110ft/lbs configuration, bolted on the ring gear (first time I've done this) and suddenly I'm up above 150ft/lbs. WTF.

The diff is held together, and all my testing has been done, with 4 m6 screws holding together the assembly. I'm guessing there's .005" or so play that's snugged up with the ring gear torqued down.

So, this morning the ring gear is coming off, and my coke can shims are going back in. Results shortly.
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Old 11-02-2012, 12:40 PM   #5
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Hey that looks familiar

Go get some stainless shim-in-a-can for final assembly and torque preloading. Comes in a bunch of thicknesses. IDK what you were going to use after mocking it up but we use that to preload transmissions and it works great.
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Old 11-02-2012, 06:59 PM   #6
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I ended up using one .015" shim.

I think it came down to dryish plates. I dipped them in gear oil* and it finally broke loose at 120ft/lbs. hopefully it'll loosen up a bit once it's soaking in the diff housing.

*they weren't exactly dry before, but not dripping in oil.

Just gotta hammer** on my new bearing and borrow a 6-7" mic.

**havent chosen my final installation method.
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Old 11-08-2012, 02:24 AM   #7
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How did you assemble your clutch packs? On the 2 OEM LSD's I took apart were like this:

Belleville washer> outer plate>inner plate>inner plate>outer plate



But from this exploded view



You can see the inner and outer plates are staggered(outer>inner>outer>inner) and the ramp is a wear surface.(which I don't like)

I am wondering if you got 3 of the 1.6mm plates if you could actually stuff one more plate in there so the stack would end up:

washer>outer>inner>outer>inner>outer
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Last edited by pitobread; 11-08-2012 at 03:02 AM.
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Old 11-08-2012, 01:34 PM   #8
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I don't think the spider gear has enough spline on it to accommodate 3 plates.

I've got pictures showing the disassembly, and mine was most definitely outer-inner-outer-inner, NOT outer-inner-inner-outer.

I'm not sure what difference it would make? I know one plate has circular groves, while the other has perpendicular groves.
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Old 11-08-2012, 04:29 PM   #9
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If there is 2 similar plates stacked together there is no friction between them so I want to put them staggered. But using the ramp surface / wear surface doesn't excite me. Hence why ideally I would like the 3rd plate.
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