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1986 325e Diff swap question

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    1986 325e Diff swap question

    Hello everyone.

    My name is Freddy and I recently acquired an all stock 1owner 1986 32e 2dr automatic with 82k on the odometer. This is my 2nd E30 (had an E30M3 that I sold a few years back). I'm looking to do a few mods to make it "peppier" around town. I already have a Turner chip installed and will eventually install an "i" head swap and possibly a manual conversion. My next mod that I'm looking to do is a diff swap but not sure what ratio to install 3.25 or 3.73. Any advice? This will be a weekend at best car but don't want it screaming on the highway too much . Thanks in advance.
    sigpic
    1988 E30 M3
    Diamantschwarz/Black

    #2
    3.25 would be a moderate improvement over the (assuming) stock 2.93, 3.73 would be pretty noticeable. Are both options limited slip? If it really is a weekend car I'd go 3.73, but that's just me.

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      #3
      Thanks...Yes this would be a weekend car at best during the summer on nice days... What model 3.73 Limited slip should I look for?
      sigpic
      1988 E30 M3
      Diamantschwarz/Black

      Comment


        #4
        IMO 3.25 is the best ratio for mixed driving. My 325is had a 3.73 from new, but it was really buzzy on the freeway over about 65mph. I like taking long road trips, so I sacrificed acceleration for high-speed comfort, and installed a 2.93 LSD. Now I can do 85 mph quite comfortably, but acceleration has tanked. 3.25 is right in the middle, so I'm thinking that's the best of both worlds. Where might I find a 3.25? I know they weren't put in many 80's-era BMW's...
        Last edited by Aleman; 06-13-2022, 11:27 AM.
        R135 /// 1990 Alpinwei├č II 325is
        └┼┼┘ /// 1993 Black/Black Convertible (sold)
        ..24

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          #5
          Originally posted by Aleman View Post
          Where might I find a 3.25?
          The Z3 M.

          Comment


            #6
            If the car itself is in good condition. Just do a manual and chip. These cars are worth a lot more (and just all around "better")if they are a gem, than a "racecar".
            john@m20guru.com
            Links:
            Transaction feedback: Here, here and here. Thanks :D

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              #7
              Originally posted by ForcedFirebird View Post
              If the car itself is in good condition. Just do a manual and chip. These cars are worth a lot more (and just all around "better")if they are a gem, than a "racecar".
              Completely agree. My car started as a stock 62,400 mile 325e, now it's a 62,600 mile car with a full turbocharged 325e driveline on standalone, and I'm going through a ton of extra effort to make it feel like a luxury comfortable car again (what these cars were supposed to be factory). My friends and I are all now adding all the creature comforts back into cars that used to be cool to remove. There's nothing wrong with having a cool, old, comfortable and modest weekend car.
              Budget E30 Parts - Used and Reconditioned parts for your BMW

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                #8
                I don't know my diff ratio no plate no numbers nothing, Running getrag 240 RPM 5th gear at 60 miles is around 2800 stock tires 185/60/14.
                Can someone guess my diff ?

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                  #9
                  Would one from a 1998 BMW Z3 1.9L MANUAL TRANSMISSION LIMITED SLIP DIFFERENTIAL 3.45 Ratio work onto my Auto ETA?
                  sigpic
                  1988 E30 M3
                  Diamantschwarz/Black

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                    #10
                    Originally posted by Shadye30 View Post
                    Would one from a 1998 BMW Z3 1.9L MANUAL TRANSMISSION LIMITED SLIP DIFFERENTIAL 3.45 Ratio work onto my Auto ETA?
                    Yes. Same diff case/cover, and mounting points. You might need need to swap the axle stubs, pretty sure the z3 used the skinny axles in the 4cyl. I know the 318ti did for sure. The stubs from your diff will work.
                    john@m20guru.com
                    Links:
                    Transaction feedback: Here, here and here. Thanks :D

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                      #11
                      Thanks ForcedFirebird.

                      Are you referring to the output flanges on either side of the differential?

                      Here is a photo of the actual part that I am looking to purchase.

                      sigpic
                      1988 E30 M3
                      Diamantschwarz/Black

                      Comment


                        #12
                        That's a small case diff, just an FYI. Most likely to be open too.
                        john@m20guru.com
                        Links:
                        Transaction feedback: Here, here and here. Thanks :D

                        Comment


                          #13
                          Originally posted by Shadye30 View Post
                          Would one from a 1998 BMW Z3 1.9L MANUAL TRANSMISSION LIMITED SLIP DIFFERENTIAL 3.45 Ratio work onto my Auto ETA?
                          I believe only 6-cylinder Z3s had Torsen and clutch LSDs.
                          You should verify it on Z3 forums.

                          Comment


                            #14
                            Good catches..thank you both..I have tracked down 2 differentials (both out of 2.5 Z3s) and not sure which one would be better for my street driven auto ETA..3.64 or 3.15..
                            sigpic
                            1988 E30 M3
                            Diamantschwarz/Black

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