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What is your ideal differential ratio for the e30

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    What is your ideal differential ratio for the e30

    Discuss the different ratios, just curious to see what everyone prefers
    4
    2.79
    50.00%
    2
    2.93
    175.00%
    7
    3.23
    300.00%
    12
    3.46
    325.00%
    13
    3.73
    525.00%
    21
    3.91
    125.00%
    5
    4.10
    125.00%
    5
    4.27
    25.00%
    1
    4.45
    50.00%
    2
    Last edited by anabolice30; 06-16-2017, 06:51 AM.

    #2
    I like my 3.25. Great on the highway but not too tall for acceleration. No 3.25 on the poll though :(

    IG @turbovarg
    '91 318is, M20 turbo
    [CoTM: 4-18]
    '94 525iT slicktop, M50B30 + S362SX-E, 600WHP DD or bust
    - updated 1-26

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      #3
      Depends on the box.

      3.91 for a G260
      3.38 for a ZF
      4.11 for the T56

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        #4
        Depends on the application. I like my 4.10 that is stock in my M3, great mileage on the freeway (31 mpg at 73 mph) its short enough to work for autoX, might be a little too tall for track use.

        Running a shorter rear end isn't a bad thing if it puts the rpm at near peak torque, that will return good fuel mileage. Lugging an engine is never a good thing. If the engine wants to be at a low rpm, then a tall rear end is great. If its a higher revving engine, let it turn some rpm.

        Match the rear end to the engine and transmission.

        Will
        '59 Alfa Romeo 101.02 Giulietta Sprint
        '69 Alfa Romeo 105.51 1750 GTV (R.I.P)
        '69 Datsun 2000 roadster Vintage race car
        '88 BMW M3

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          #5
          I like the 3.15 gearing in our 330i - but it has lots of torque and a 6 speed. You don't get to shift all that much, but it's creamy smooth as a DD. I don't like the gearing in our xi, it has the same motor but it's just too short (I think 3.38 or something) - for whatever reason, it makes it feel a little gutless.

          When my M20 was healthy, the 4.10 was a lot of fun - would still hit ~60 at 7500rpm in 2nd gear, so it wasn't really "short". However, I'll probably want something longer eventually when I finally get a new motor in there.. I mostly just cruise in it now, and the 4.10 does get a bit tiring on the freeway after a while.
          Build thread

          Bimmerlabs

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            #6
            Where is the 3.15 Torsen??? I think thats the ideal ratio for a 24v swap car with a ZF. With that being said I am running a 2.93 LSD.

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              #7
              Final ratio depends entirely on how much hp your engine is putting out and where.
              AWD > RWD

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                #8
                I'm okay with the 3.64 LSD, but I'd probably be a bit happier with taller gearing to bring the revs down when cruising the freeway. Gets a little droney and I'd like better gas mileage on road trips.
                "Leafeon" '92 Lagunengrun 325i Vert (Daily Driver/Project)
                http://www.r3vlimited.com/board/showthread.php?t=366044
                The stickers make it go faster. :nice:

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                  #9
                  Originally posted by BlackbirdM3 View Post

                  Match the rear end to the engine and transmission.
                  If it's got tits or tires, it's gonna cost ya!

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                    #10
                    3.46 but that is because of the S54, I do like the 4.10 my car has now though.
                    Euro Delivery Thread///E30 Project Klaus///COTM August 2021

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                      #11
                      3.15 Torsion in my 318i was ideal on the highway.

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                        #12
                        i put a 2.93 lsd in my 93 octane chipped mtech II cabby to improve the mileage a bit. i removed a 4.10 and went from about 21 to 26. this is verified over several tank fulls by dividing the miles driven by gallons filled. it worked out fine in houston. a bit doggy but not too bad because sea level and its flat as hell here.

                        i took the car to denver and i have to say that ratio is a poor choice for this area of the country. i do not recommend it with an m20 at high altitudes and hilly terrain.
                        sigpic
                        Gigitty Gigitty!!!!

                        88 cabrio becoming alpina b6 3.5s transplanted s62
                        92 Mtech 2 cabrio alpinweiss 770 code
                        88 325ix coupe manual lachsilber/cardinal
                        88 325ix coupe manual diamondschwartz/natur
                        87 e30 m3 for parts lachsilber/cardinal(serial number 7)
                        12 135i M sport cabrio grey/black

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                          #13
                          I kept the 4.10 in my vert when I changed it to a 5 speed. I'm around 3500 at 65 and top out at 120.. I do have a 240 in it ment for the 320i and 324d. I do like it for the hilly region I live in. But often thought about going up to a 3.73 gear.

                          1992 BMW 325iC
                          1978 Chevrolet Monte Carlo
                          1965 Chevrolet Corvair Monza 140hp

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                            #14
                            I have a 2.93 LSD in my ZF trans car
                            sigpic

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                              #15
                              Running the 3.15 Torsen in mine w/ the s52 and ZF trans. It's great around town, but to my surprise, still a bit 'much' on the highway. A 2.93 would probably suit it better. But - since I want to keep the Torsen, I think a 6 speed will be coming in the future. Still has the 1:1 5th gear and I have the option for the overdrive in 6th if I'm doing highway cruising.
                              -Geno

                              '87 325is (s52'd)
                              '95 525iT
                              '02 Range Rover 4.6 HSE
                              '98 Disco 1

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