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e30 g240 selector rod joint - ditch the foam for washers? Tell me why this is dumb.

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    e30 g240 selector rod joint - ditch the foam for washers? Tell me why this is dumb.

    I'm rebuilding all the shift components on my 91 318is, and one of the commonly suggested parts to replace is #14 in the diagram, the "gearshift rod joint", part number 25117503525.




    This is an all metal part without bushings - but it does contain a little foam spongy disk that cushions the movement of the joint against the selector arm exiting the transmission casing. On my 22 year, 200k mile old car, the foam piece inside had completely disintegrated into particles of oil soaked crud. There would be the contribution of the #14 joint to shifter slop.

    So this was among the parts I ordered for the job. I used realOEM.com to get the part number. What I got, is not what I ordered. I got a bag with part number 25117503525, which is the right number, and inside that bag, another bag labeled 25 11 1 203 682 - which is similar but with a different design. You can see the difference in this picture - old on the right, new on the left.



    Two major differences - the new design isn't cylindrical where it attaches to the transmission, using a wire clip rather than a ring-like tension bushing (#19) to hold the dowel pin in place. The other difference is that the welding between the two sections is much stronger on the new part. Both are good changes, but i'm a little annoyed that I bought a tension bushing when I didn't need to, not being informed of the changed part.

    So here's my possibly dumb idea.

    The joint comes with a new foam pad pressed in (another part, #20, that I ordered separately, needllessly, because the #14 joint itself wasn't shown to come with one from the vendor I purchased it from). The pad will allow some movement, and probably helps to damp said movement. But even a brand new pad will eventually wear, and it can't really take that long.

    I popped out the foam pad and dropped in a couple lock washers





    they come up to just past the hole the dowel slides through.




    If I press the joint onto the selector arm and slide in the dowel, it should create an interference fit, with the tension of the lock washers allowing for some movement (albeit more resistant than the foam) but without vibration, since the washers will maintain contact with the two surfaces at all times.

    Because I'm not going to want to redo it, I'm trying to think of reasons why this wouldn't work. Got any?

    On the other hand, I'm not going to want to redo it, so telling myself "Bmw used the pad, the pad must work, use the pad" hasn't convinced me, because the pad is not the sort of medium I can see holding up for any appreciable length of time. Age and mileage taken into account, the remnants of the original pad don't show a durable part. And it would certainly numb up the shifter feel some amount greater than none.

    91 318is build thread

    #2
    Use the pad. You would not even be able to assemble it with the lock washers in there.

    That piece rotates on the pin when you move the shifter side to side, a lock washer would destroy the ball end of the shift shaft.
    Lorin


    Originally posted by slammin.e28
    The M30 is God's engine.

    Comment


      #3
      Cool, that's the kind of reason I was looking for. Still wish it was a design that could be permanent, or longer lasting, like say a low durometer poly bush. But at least I'm using those everywhere else that I can. Thanks Lorin!

      91 318is build thread

      Comment


        #4
        Yep, I did this & used the foam pad. I also put in a short throw shifter & replaced #2 & the contact portion of #4 with Garagistic's delrin pieces. Shifter is awesome now.

        Sent from my SGH-T989 using Tapatalk

        Comment


          #5
          Good to hear - I'm using a hybrid ebay SSK (B&M style aluminum cup, see my build thread if interested) with the garagistic carrier bushings at the front and rear, and a new #8 rubber boot.
          And it'll have a 22 year old shift boot with an utterly trashed stock knob. Until I've got all my new interior parts ready to swap in.

          91 318is build thread

          Comment


            #6
            It would seem to me that the ball end and the cross pin take the shifter loads. The foam pad then is to reduce vibration and wear.
            The car makes it possible, but the driver makes it happen.
            Jim Levie, Huntsville, AL

            Comment


              #7
              I deleted the pad entirely... Maybe I'm just stupid, though. I don't see how it has any effect on shifting mechanism as it isn't load bearing at all.
              '84 318i M10B18 147- Safari Beige
              NA: 93whp/90ftlbs, MS2E w/ LC, 2-Step
              Turbo: 221whp/214ftlbs, MS3x flex @ 17psi

              Comment


                #8
                if that is the case, then that part (the kunckle as a whole) shouldn't make an appreciable difference when replaced, and yet I've seen several people say that it's one of the most important. I think that the foam pad is meant to expand to fill in the gaps that would normally exist when axial force was exerted.

                I guess the way to tell would be to try it with and without the pad when everything was new, and see the difference. I'd do that if I hadn't installed/removed my setup 3-4 times before getting it where I wanted it...

                91 318is build thread

                Comment


                  #9
                  You can cut a piece from a rubber racquet ball as a long lasting substitute for the foam pad.

                  Comment


                    #10
                    Originally posted by cunninglinguist View Post
                    You can cut a piece from a rubber racquet ball as a long lasting substitute for the foam pad.
                    ha, that's kind of brilliant

                    91 318is build thread

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