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M3 Track: Racing and DE Best mod for speed is learning to get the most out of what you currently have. Tracks and DE's is the place to start!


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Old Tue, Oct-29-2019, 10:03:22 PM   #11
aeronaut
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Default Re: Differentials

Sub'd also. I have a blown one (E36) sitting on my floor in the shop. I've pulled some of the bearings, but the DIY route looks daunting.
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Old Wed, Oct-30-2019, 02:40:42 AM   #12
bigjae1976
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Default Re: Differentials

I have the 4 clutch racing diffs kit. Still in progress...havenít had any time to finish it.

You need the Belleville springs but you can reuse the old ones. Racing diffs sells new stiffer springs for more preload.

Itís actually pretty straight forward to assemble the LSD unit. The hard part is disassembly and assembly of the diff...removing the bearings and races.

I have a zf Unit from an M635CSi. It comes with equal length half shafts. You can also get an extra long E46 M3 half shaft and cut it down.


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Old Wed, Oct-30-2019, 02:40:44 PM   #13
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Default Re: Differentials

Here's some more info on different units, you'll have to translate from German:
http://www.m3racing.de/sperre.html

ZF vs OS Giken (for Porsches, but same principles apply):
http://forums.pelicanparts.com/porsc...-os-giken.html

Some more discussion on different LSD's, with Paul Guard of Guard Transmission chiming in:
https://rennlist.com/forums/porsche-...d-to-have.html

Last edited by CrookedCommie; Wed, Oct-30-2019 at 05:19:45 PM.
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Old Wed, Oct-30-2019, 03:08:15 PM   #14
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Default Re: Differentials

Quote:
Originally Posted by CrookedCommie View Post
Here's some more info on different units, you'll have to translate from German:
http://www.m3racing.de/sperre.html
Florian has put together a TON of info, especially for the E92 side of things over the years, it's a great resource! Same guy that runs limitedslip.de
I'd talked to him a bit over a year ago regarding what he recommends. Generally, if you got the money, he said Drexler. His custom diffs are really nice as well, great value for money. That said, they'll also require different output shafts since it's based on the ZF units.

For me, he recommended:
  • Drexler clutch-type LSD with "GT race light" Setup and drilled clutches
  • Set of new drive flanges (symmetric to fit clutch lsd)

Those parts were roughly 2500 Euros. Add another 200 Euros for US shipping and it gets money quick :-(

I'll try to go back and translate that site when i get off work though.
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Old Wed, Oct-30-2019, 05:21:49 PM   #15
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Default Re: Differentials

Has anyone here switched from the factory LSD to an aftermarket LSD with tangible results? I.e. lap time reduction. I don't doubt that a clutch-type LSD is better, but for the amount of money we're talking about, "better" needs to be substantial and measurable. in my opinion, anyway. I realize LSD swaps are often combined with gear ratio changes and I think it might be difficult to extract the improvement from the LSD alone.
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Old Wed, Oct-30-2019, 06:07:34 PM   #16
CrookedCommie
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Default Re: Differentials

With the stock diff, my car is not stable on corner exit or braking, and I can't get on throttle early enough compared to some of my peers in different cars running similar tire compounds. I don't have any data but my guess is that a properly working LSD, not just in combination to a gear change, could have 1-2 seconds difference on a 2 mile circuit.

Here's a research paper showing how an optimized LSD vs Open Diff can have .2 seconds difference in time just over one 25ft lane-change type corner. Specifically look at Section 3.2: Optimal LSD Solution
https://www.tandfonline.com/doi/full...4.2015.1093150
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Old Wed, Oct-30-2019, 06:23:48 PM   #17
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Default Re: Differentials

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Originally Posted by CrookedCommie View Post
Here's a research paper showing how an optimized LSD vs Open Diff can have .2 seconds difference in time just over one 25ft lane-change type corner. Specifically look at Section 3.2: Optimal LSD Solution
https://www.tandfonline.com/doi/full...4.2015.1093150
holy crap, this is fantastic! Thanks for the link
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Old Wed, Oct-30-2019, 06:40:00 PM   #18
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Default Re: Differentials

Quote:
Originally Posted by Tinnit View Post
Has anyone here switched from the factory LSD to an aftermarket LSD with tangible results? I.e. lap time reduction. I don't doubt that a clutch-type LSD is better, but for the amount of money we're talking about, "better" needs to be substantial and measurable. in my opinion, anyway. I realize LSD swaps are often combined with gear ratio changes and I think it might be difficult to extract the improvement from the LSD alone.
We saw tangible results in our data after switching to an ATS diff, but I can't say for sure that they translated directly to lap time improvements other than making the car easier to drive. you can see the data in post 71 of my build thread.
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Last edited by klodkrawler05; Wed, Oct-30-2019 at 06:43:32 PM.
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Old Thu, Oct-31-2019, 01:31:40 AM   #19
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Default Re: Differentials

Iíve driven a Metric Mechanic ZF clutch diff in my 330 and then the M lock in my M3.

The ZF was much more responsive. Iíd say the difference is when you get on the throttle and youíre throttle steering. Itís way easier to get it right with the ZF unit than the M Lock. I always felt like I was telling what my 330 to do with the throttle. My M3 feels like Iím in a constant argument and there is a lack of cooperation.

Iíll come out of a corner in a tank slapped with my M3 whereas my 330 would slide, catch and go.


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Old Thu, Oct-31-2019, 03:44:34 PM   #20
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Default Re: Differentials

Quote:
Originally Posted by bigjae1976 View Post
Iíve driven a Metric Mechanic ZF clutch diff in my 330 and then the M lock in my M3.

The ZF was much more responsive. Iíd say the difference is when you get on the throttle and youíre throttle steering. Itís way easier to get it right with the ZF unit than the M Lock. I always felt like I was telling what my 330 to do with the throttle. My M3 feels like Iím in a constant argument and there is a lack of cooperation.

Iíll come out of a corner in a tank slapped with my M3 whereas my 330 would slide, catch and go.


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take out that friction modifier
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Discussing Differentials in the M3 Track: Racing and DE Forum - Best mod for speed is learning to get the most out of what you currently have. Tracks and DE's is the place to start! at BMW M3 Forum.com (E30 M3 | E36 M3 | E46 M3 | E92 M3 | F80/X)