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    Gearing Change 2.93 to 3.45/3.15 etc

    Hey there,

    So I've researched quite a bit and know that the lower ratio (below 3.07 gear ratio) can't simply swap the ring and pinion gears to a higher ratio (such as a 3.15/3.45/3.73 etc) as there will be a gap and the ring and pinion won't be properly seated.

    I've also found that people install extra shims to bridge that gap.

    My question, hopefully for the differential/gearing guru's... I've got my eye on a spacer kit that bridges that gap (will post a link to it), and a set of 3.45 ring and pinion gears for my medium case differential. With the spacer kit and the gears, would I be able to essentially swap this into my medium case differential? Or maybe only do the ring gear and leave the pinion installed, as is?

    I have a 1987 325es with the 2.93 LSD gears. Even with the turbo it's still way too long.

    Links below are what I have my eye on, just wondering if it's a waste. I'm also eyeing up the 3.25 gear sets, or a 3.25 rear end but the only ones I'm finding complete are unknown history and like $550 shipped to me.

    The website is: racingdiffs.com .. below are the links for their eBay posts.

    Gear Set: (This company has 3.15/3.25/3.45/3.73/3.91,etc)



    Spacer Kit:

    # BMW, gear ratio, tds, swap, distance, spacer, ring gear, crown gear, high to low gear ratio, carrier, 188mm, motorsport, e36, e34, e30. As you know, it is lot easier to source used Limited slip differential from TDS models.


    Hate to buy anything on eBay but the seller seems to know what he's talking about and seems to have solid reviews.

    Really appreciate any help, TIA!
    Last edited by E30-Ellerman; 11-22-2018, 10:22 PM.
    2016 F-150
    1987 Royalblau 325es B25 turbocharged

    Build thread here: http://www.r3vlimited.com/board/showthread.php?t=405594

    #2
    Originally posted by E30-Ellerman View Post
    Hey there,

    So I've researched quite a bit and know that the lower ratio (below 3.07 gear ratio) can't simply swap the ring and pinion gears to a higher ratio (such as a 3.15/3.45/3.73 etc) as there will be a gap and the ring and pinion won't be properly seated.

    I've also found that people install extra shims to bridge that gap.

    My question, hopefully for the differential/gearing guru's... I've got my eye on a spacer kit that bridges that gap (will post a link to it), and a set of 3.45 ring and pinion gears for my medium case differential. With the spacer kit and the gears, would I be able to essentially swap this into my medium case differential? Or maybe only do the ring gear and leave the pinion installed, as is?

    I have a 1987 325es with the 2.93 LSD gears. Even with the turbo it's still way too long.

    Links below are what I have my eye on, just wondering if it's a waste. I'm also eyeing up the 3.25 gear sets, or a 3.25 rear end but the only ones I'm finding complete are unknown history and like $550 shipped to me.

    The website is: racingdiffs.com .. below are the links for their eBay posts.

    Gear Set: (This company has 3.15/3.25/3.45/3.73/3.91,etc)



    Spacer Kit:

    # BMW, gear ratio, tds, swap, distance, spacer, ring gear, crown gear, high to low gear ratio, carrier, 188mm, motorsport, e36, e34, e30. As you know, it is lot easier to source used Limited slip differential from TDS models.


    Hate to buy anything on eBay but the seller seems to know what he's talking about and seems to have solid reviews.

    Really appreciate any help, TIA!


    Unknown history complete diff would be the more reliable way to go; If budget allows a zero mile diff built to spec would be best.

    Built enough national championship winning actual race use differentials and street car units to be able to state this as fact.

    Random cheap parts for internal drivetrain use from Eastern Europe would not be the smart/simple way to fix your problem; it’s not cost effective either if on a budget and have limited skills.





    Sent from my iPhone using Tapatalk
    OBD1 M54/M52TU swap as a M50b25

    Z4 non powered steering rack fits e30



    Euro e46 2005/6 320d 6mt gearbox into E30 with M20 hardy and beck 1985 327s engine

    Comment


      #3
      Originally posted by Wanganstyle View Post
      Unknown history complete diff would be the more reliable way to go; If budget allows a zero mile diff built to spec would be best.

      Built enough national championship winning actual race use differentials and street car units to be able to state this as fact.

      Random cheap parts for internal drivetrain use from Eastern Europe would not be the smart/simple way to fix your problem; it’s not cost effective either if on a budget and have limited skills.





      Sent from my iPhone using Tapatalk
      Thank you for the reply. Really gives good insight from someone who has specific experience. The buying the spacer kit and tossing in the gear is the cheaper option, but think I’m going to wait to find a 3.25 locally or order online if I can’t find local.

      Thanks again. Anyone else try doing the extra shims or spacers to re gear it?
      2016 F-150
      1987 Royalblau 325es B25 turbocharged

      Build thread here: http://www.r3vlimited.com/board/showthread.php?t=405594

      Comment


        #4
        Also, hopefully someone has an answer. I have a line on a 1985 735i automatic differential for cheap. It's complete and still in the car. If this is a medium case, 6 bolt diff, what would the final gear ratio be on that? I'm finding 3.25, 3.64, 3.91, etc... most seem to be 3.25.

        Thank you
        Last edited by E30-Ellerman; 11-25-2018, 06:41 PM.
        2016 F-150
        1987 Royalblau 325es B25 turbocharged

        Build thread here: http://www.r3vlimited.com/board/showthread.php?t=405594

        Comment


          #5
          Originally posted by E30-Ellerman View Post
          Also, hopefully someone has an answer. I have a line on a 1985 735i automatic differential for cheap. It's complete and still in the car. If this is a medium case, 6 bolt diff, what would the final gear ratio be on that? I'm finding 3.25, 3.64, 3.91, etc... most seem to be 3.25.

          Thank you


          Realoem.com

          Last 7 digits of vin.
          OBD1 M54/M52TU swap as a M50b25

          Z4 non powered steering rack fits e30



          Euro e46 2005/6 320d 6mt gearbox into E30 with M20 hardy and beck 1985 327s engine

          Comment


            #6
            Thanks!

            Real oem says 3.46! Now if it’s an LSD and I can get it for cheap, might be a good find!
            2016 F-150
            1987 Royalblau 325es B25 turbocharged

            Build thread here: http://www.r3vlimited.com/board/showthread.php?t=405594

            Comment


              #7
              Originally posted by E30-Ellerman View Post
              Hey there,

              So I've researched quite a bit and know that the lower ratio (below 3.07 gear ratio) can't simply swap the ring and pinion gears to a higher ratio (such as a 3.15/3.45/3.73 etc) as there will be a gap and the ring and pinion won't be properly seated.

              I've also found that people install extra shims to bridge that gap.

              My question, hopefully for the differential/gearing guru's... I've got my eye on a spacer kit that bridges that gap (will post a link to it), and a set of 3.45 ring and pinion gears for my medium case differential. With the spacer kit and the gears, would I be able to essentially swap this into my medium case differential? Or maybe only do the ring gear and leave the pinion installed, as is?

              I have a 1987 325es with the 2.93 LSD gears. Even with the turbo it's still way too long.

              Links below are what I have my eye on, just wondering if it's a waste. I'm also eyeing up the 3.25 gear sets, or a 3.25 rear end but the only ones I'm finding complete are unknown history and like $550 shipped to me.

              The website is: racingdiffs.com .. below are the links for their eBay posts.

              Gear Set: (This company has 3.15/3.25/3.45/3.73/3.91,etc)



              Spacer Kit:

              # BMW, gear ratio, tds, swap, distance, spacer, ring gear, crown gear, high to low gear ratio, carrier, 188mm, motorsport, e36, e34, e30. As you know, it is lot easier to source used Limited slip differential from TDS models.


              Hate to buy anything on eBay but the seller seems to know what he's talking about and seems to have solid reviews.

              Really appreciate any help, TIA!
              Don't understand why the 2.93 would be too tall for turbo use. I run 2.65 in my m52 turbo and it's perfect. But if some want's to swap the tall ratio LSD to short ratio LSD I'm more than happy to ship my short ratio LSD in exchange of tall gear one. The medium case short ratio LSD units are "cheap" and plentiful here but tall ratio ones are non existent.

              Comment


                #8
                Originally posted by pazi88 View Post
                Don't understand why the 2.93 would be too tall for turbo use. I run 2.65 in my m52 turbo and it's perfect. But if some want's to swap the tall ratio LSD to short ratio LSD I'm more than happy to ship my short ratio LSD in exchange of tall gear one. The medium case short ratio LSD units are "cheap" and plentiful here but tall ratio ones are non existent.
                I guess I just don't have enough power. It doesn't hit very hard when the turbo kicks in, just kind of linear power and not a ton of it. Perhaps I'll get my boost controller installed and head for a dyno tune before changing out the diff settings. I have a quite conservative tune at 11 psi now.
                2016 F-150
                1987 Royalblau 325es B25 turbocharged

                Build thread here: http://www.r3vlimited.com/board/showthread.php?t=405594

                Comment


                  #9
                  Originally posted by pazi88 View Post
                  Don't understand why the 2.93 would be too tall for turbo use. I run 2.65 in my m52 turbo and it's perfect. But if some want's to swap the tall ratio LSD to short ratio LSD I'm more than happy to ship my short ratio LSD in exchange of tall gear one. The medium case short ratio LSD units are "cheap" and plentiful here but tall ratio ones are non existent.


                  Do you have a zf 5 speed or g260 5mt?

                  The zf5 has a 1:1 5th gear = the g260 4th.
                  OBD1 M54/M52TU swap as a M50b25

                  Z4 non powered steering rack fits e30



                  Euro e46 2005/6 320d 6mt gearbox into E30 with M20 hardy and beck 1985 327s engine

                  Comment

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