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M3 Diff????

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  • M3 Diff????

    Does this look like a M3 Diff??
    Mine is aluminum colored
    Can buy it at a good price but I'm not sure this is right.


  • #2
    It does look like an M3/325 e30 diff. The 318 is narrower. If yours is made from aluminum, then it must be a rare race part. The steel case is very heavy.

    [email protected]

    1969 2002 racecar
    1989 M3 racecar
    e39 Touring


    • #3
      It certainly does - I've got one in bits on the bench at the moment and it does look the same.
      Scottish Cecotto


      • #4
        Looks more of a 325 diff. without LSD to me. M3 diff. is more bulky having LSD and has "S" mark in white paint on the top and bottom of the case which denotes Limited Slip Differerential. If it does not have this mark, then its a 325 diff. This, however will fit into your M3. I have done this kind of swap already.



        • #5
          Of the many LSD's I've looked at over the years I've only seen one that still had a visible "S". So if it's not there no biggy.

          The easiest check to confirm whether or not it's LS is to simply try to rotate the output flanges opposite from each other by hand. The outcome will make it obvious what you have.

          Keep in mind this will not tell you if the LS unit is 100% functioning, but it will tell you what it's supposed to be. However, a toasted LSD will feel like an open diff (and in that case you wouldn't want it anyway). I own one and can attest to its toastyness.

          What this picture shows is that it's a medium sized diff and that's all. All small and medium diffs fit and I believe the large diff (5er) will fit as well but with some modifications (never tried it though). The fact that this one has the medium case does not mean it has LS however, or what it came out of. This is simply the case used on all E30 6cyl cars and the M3. (I can't remember, but the 318iS may have got the medium case as well).

          The ratio will give you a clue as to what it most likely came from. The E30 M3's ratios were only 3.15, 3.25 (Euro only) and 4.10 (US only). Anything else and it's not from an M3. But the point I'm trying to make is that it doesn't really matter what it came out of, as long as it has a functioning LS unit and it's the ratio you desire.

          Jake Larsen
          Last edited by Jake; 04-06-2004, 10:51 PM.


          • #6
            the seller confirmed the it was removed from his M3. He is swapping for s50 so he had to change the diff. The gear is 4.10 and the LSD wont be used since I put in a Quaife.

            Thanx all for clearing my doubts!


            • #7
              Stevem, you managed to source a diff then? good stuff. What are you doing with yours, have you stripped it?


              '90 M3
              '58 Austin Healey Sprite
              '02 Suzuki SV650S


              • #8
                I'm in the middle of doing my diff - I've just come in for a cup fo tea.

                I got a used diff from an M3.

                I've tested the break-away torque (using a torquw wrench on one output shaft, with the other in the vice).

                The replacement diff (around 65000miles) gave 51 lb/ft

                My original diff gave 42 lb/ft

                What are they supposed to be? And what can you go up to without giving serious understeer under turn-in?

                Mags, I should have taken you up on your offer of a loan diff while I get mine rebuilt. The one I got was 350 plus VAT and shipping! Hopefully the 50 lb/ft will be better, but I plan to strip mine down and try shimming it up to increase the breakaway.

                What a pg to remove the diff! The four bolts holding the diff onto the cross-member where a pain to get to. All in, about 1 1/2 hours to get the old one out. Hopefully the rain will stop and I'll get the other unit back in this afternoon.

                One way or the other, I'm going to have a spare 3.25 LS diff for sale soon!
                Scottish Cecotto