Rebuilding BMW/ZF 188mm Limited Slip (25% -> 40% lock)

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Jon K
Posts: 602
Joined: Fri Dec 04, 2009 1:45 am
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Rebuilding BMW/ZF 188mm Limited Slip (25% -> 40% lock)

Post by Jon K »

This is real simple. For my turbo car I rebuilt one going from 25% to 60% lock by machining and fitting 4 clutches/dog plates in place of 2. For my daily driver '95 525i I decided to fit an LSD diff and rebuilt it for 3 clutches/dog plates which will result in a more calm 40% lock up. 60% is nice in the turbo car but tight radius turns result in tire chatter since the axles are so locked.

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'93 3.23 LSD Differential by Jon Kensy, on Flickr

Old clutches were in good shape:

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IMG_0055.jpg by Jon Kensy, on Flickr

Replacement clutch set:

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BimmerDiffs.com 3-Disc Upgrade by Jon Kensy, on Flickr

You just remove the end plates and then remove the ring gear/LSD carrier. You make sure that your carrier depth is ~96.8mm and your LSD cover plate is about 14.0x mm inset. Then, just swap out a spacer plate and old clutch/dog plates with new. ZF used a spacer in the diff that can be removed and is the exact same thickness as an additional clutch/dog plate. So, going from 2 clutch to 3 clutch is easy. 2 clutch to 4 clutch required machining down the carrier cover by the stack thickness difference, still not hard, though.

Old parts out:

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3.23:1 LSD 40% Lock-up Setup by Jon Kensy, on Flickr

Measuring backlash:

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3.23:1 LSD 40% Lock-up Setup by Jon Kensy, on Flickr

Spec is 0.06 - 0.014mm (0.0023 - 0.0055"). Mine measures in at 0.0041", well within spec.

Measuring backlash:

[vimeo]56961733[/vimeo]
1992 700RWHP Pump Gas BMW
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Simon P.
Posts: 96
Joined: Sat Nov 12, 2011 6:24 pm
ECU Model: S100 Pro
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Location: Montreal, Canada

Re: Rebuilding BMW/ZF 188mm Limited Slip (25% -> 40% lock)

Post by Simon P. »

Nice Jon,
I did the same (3 clutch mod) with my 4.10 e30 diff in my ti. Did you use thicker Porsche plates or the stock thickness BMW plates? I went with 2.1mm Porsche Motorsport dog ear plates rather than the standard 2.0mm BMW ones for a bit more lock-up.
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Jon K
Posts: 602
Joined: Fri Dec 04, 2009 1:45 am
ECU Model: S80 Pro
Distributor: DTA UK
Firmware Version: 73
Location: Pennsylvania, USA
Contact:

Re: Rebuilding BMW/ZF 188mm Limited Slip (25% -> 40% lock)

Post by Jon K »

Simon I used a kit from www.bimmerdiffs.com they measure a hair over 2.0mm
1992 700RWHP Pump Gas BMW
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Dta2016
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Re: Rebuilding BMW/ZF 188mm Limited Slip (25% -> 40% lock)

Post by Dta2016 »

I need to rebuild my e46 m3 diff it's knocking like crazy the oil leaked out, I wonder if they have any rebuild kits for mine.
Simon P.
Posts: 96
Joined: Sat Nov 12, 2011 6:24 pm
ECU Model: S100 Pro
Firmware Version: 61
Location: Montreal, Canada

Re: Rebuilding BMW/ZF 188mm Limited Slip (25% -> 40% lock)

Post by Simon P. »

The E46 M3 uses the larger 210mm unit and they are rebuildable. Contact Dan at Diffsonline (http://diffsonline.com/) and he should be able to help you out.
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