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  • LSD ratio change

    Hi all.
    I was hoping if someone can tell me if it's possible to change the ratio on your diff by changing the gears in the diff?

    Or can the LSD be put into an open diff.

    And can it be done at home or is it a professional only job.

    Thanks in advance
    Titan Silver 1999 M Coupe

  • #2
    The rear gear ratio is indeed just down to the crown wheel and pinion.
    However, setting these up accurately is complex, with the correct degree of mesh needed and the contact points in the right part of the teeth. I do all my own work but would leave this to a pro diff shop (not a BM dealer, as I'm sure they would sub-contract it too). If you get it wrong it'll whine and wear quickly.
    Easiest option is a simple diff swap for a different ratio.

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    • #3
      As above, it's a tricky job that few garages would have the real knowledge to do properly. I've also heard of builds that turned out noisy from apparently known diff builders.

      You can use most open diff gearsets from E24, E28, E30, E36, E34, Z3 etc, so if you find the ratio you want in an open diff, this can be transferred to your LSD diff, but it would essentially be a rebuild to fit it.

      The Z3M LSD is "best" version of the E30 style diff, it is stronger than the E30 LSDs and uses different design ramps etc. That said I've been running a 3.45 LSD off an old E30 for a few years now without problems.

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      • #4
        I want a 3.64 and I know the e30s had these but don't fancy having a diff from such an old car in mine(probably never had it's oil changed) in my car.

        Does anyone know the approximate cost of a rebuilt to the ratio I want.

        Thanks again guys for the advice it's really appreciated
        Titan Silver 1999 M Coupe

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        • #5
          Try this company who offer rebuilds and also sell complete diffs

          http://www.automac.co.uk/product/LSD-3.64%20E30

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          • #6
            Thanks mate I will give them a call tomorrow or monday
            Titan Silver 1999 M Coupe

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            • #7
              Yea 3.64 diff is perhaps the most common E30 LSD ratio. Diff change isn't too bad, might be worth getting the diff and running it (change oil etc and swap backplate) to see how it is before opening both diffs up.

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              • #8
                Sounds like good advice I might do that.

                Always been worried about diffs. 1 year at Santa pod I seen a e30 touring rev and break his diff. Poor guy never got off the line
                Titan Silver 1999 M Coupe

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