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    Help! What gearbox

    Hey so I'm about to start putting my m50 into the e30 and I don't know what gearbox to use... I've got a g240 that's currently in the car but needs a new input shaft bearing.... I also have a g260 sitting in the garage.

    I don't know what it's going to cost to get the bearing repairs once I take it out of the car compared to the effort in fabricating a trans mount and bending shifters on the g260.

    Is it worth going to the effort of the g260 when running an m50 with cans, chip and head work? Or will the 240 be ok and I sell the g260 and spend the money on an lsd?

    Thanks
    Blake

    #2
    you have a g260 in the garage...Use that one. That would be the simplest and most cost effective solution. If you really want to spend some money, a ZF would be a better option, but again, you have a g260 already...

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      #3
      Get a ZF box from m50 or m52, closer ratios, stronger and smoother shifting newer box. Or a wide ratio ZF box from m51 diesel if you had those, this will get you short first gears for hooning and normal 5th for the highway. Don't see keeping the old Getrag reasonable once it is out of the car.
      My transaction feedback on r3vlimited :):Clickety click

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        #4
        If you can swing it, I vote for the ZF also.

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          #5
          Does the ZF work with the M20 clutch and flywheel?

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            #6
            Yes, the ZF works with the m20 clutch/flywheel combo. You'll need the m20 flywheel (with back side shaved to clear the oil pan), m20 starter, m20 clutch kit (including m20 throwout bearing). You'll need the ZF pilot bearing however, and ZF slave cylinder (from a 328i(s) or M3). This setup does require using a 328i or M3 4 bolt driveshaft with an e30 CSB installed. Rear end ratio should be between 2.93 and 3.25 for a street car due to the 1:1 5th gear.

            If you want to use the G260, then you can stick to using standard m20 parts as would be found in a 325i, but the transmission requires a custom brace because the transmission is rotated 10 degrees (they're about 75 dollars from various vendors). The downside to this setup is that the g260 blocks the two rear most oil pan bolts, so unless you drill access ports in the bellhousing, removing the 24v pan would require removing the transmission. For the g260, rear end ratios are usually between 3.73 and 4.10 as found in an m20 325i since 5th gear is an overdrive.

            The g240 isn't very strong, and is really only suited for the low torque of the m42, so no point putting that transmission behind any of the 24v engines.

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              #7
              Yeh right! I think i'll stick with the 260 for now then because I've got the pilot bearing and all the other bits and pieces to make the getrag work.....

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                #8
                Originally posted by mtech325 View Post
                Yes, the ZF works with the m20 clutch/flywheel combo. You'll need the m20 flywheel (with back side shaved to clear the oil pan), m20 starter, m20 clutch kit (including m20 throwout bearing). You'll need the ZF pilot bearing however, and ZF slave cylinder (from a 328i(s) or M3). This setup does require using a 328i or M3 4 bolt driveshaft with an e30 CSB installed. Rear end ratio should be between 2.93 and 3.25 for a street car due to the 1:1 5th gear.

                If you want to use the G260, then you can stick to using standard m20 parts as would be found in a 325i, but the transmission requires a custom brace because the transmission is rotated 10 degrees (they're about 75 dollars from various vendors). The downside to this setup is that the g260 blocks the two rear most oil pan bolts, so unless you drill access ports in the bellhousing, removing the 24v pan would require removing the transmission. For the g260, rear end ratios are usually between 3.73 and 4.10 as found in an m20 325i since 5th gear is an overdrive.

                The g240 isn't very strong, and is really only suited for the low torque of the m42, so no point putting that transmission behind any of the 24v engines.
                Thanks for all the insight!

                With the ZF do you know if a 87 325e driveshaft would work?

                Also that rear end seems like an awfully low ratio for a M50, I'm planning on 3.73 in my M52... Maybe 3.25 with a S50/2 I thought?

                Comment


                  #9
                  If it's the large flange 325e driveshaft, then it should work. I don't know the exact year range they were produced though. Quick searching comes up with production dates of 9/85-9/86, but I can't confirm that.

                  As for the rear end ratios, a ZF with anything above a 3.25 is going to be revving fairly high on the freeway. I currently have a 3.23 Z3 diff in my m50 with a ZF and it spins just shy of 3500 RPM at 80 mph. A 3.73 behind a ZF is going to be very aggressive. I've personally tried this, and by 5th gear the car was spinning 4,000 RPM at 70 mph on stock diameter wheels and tires (however it was fun burning out into 3rd gear). If it's strictly a track/autocross car you're building, then by all means go for it.

                  I agree that a 2.93 is probably a little conservative for an m50, but not all the e36 diff ratios are readily available in the e30 diff casings. An m50 out of an e36 typically comes with a 3.15, but to find that ratio in a diff that will fit an e30 means sourcing a torsen from a z3, or clutch style LSD from an s54 z3M (which is even rarer). Granted it has more torque than an m50, manual m52 powered e36's came with 2.93 rear ends, and they're plenty zippy. That's most likely why the 2.93 and 3.25 diffs are popular options as there were enough 325 etas and e28 cars that came equipped with these diffs, but even now they're becoming harder to find.

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