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Thumping in Center Console - M30B35 swapped into E30

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    Thumping in Center Console - M30B35 swapped into E30

    Hi, just looking for help in determining where a thumping sound is originating from.

    Background:
    My sons each have an e30 coupe that we have completely redone and swapped M30B35s into. Both have been running great for a couple of years now, however 2 weeks ago the 1987 coupe started to make a thumping sound that seems to transfer into the cab area thru the centre console and we are struggling to find the cause/cure.

    Symptoms:
    1) The thumping appears to be transferring into the cab area thru the drive shaft centre bearing bracket.
    2) It occurs around 2,000 to 2,600 rpm when the motor is under load. The sound seems to disappear above and below these rpms.
    3) The thumping increases and decreases inline, more or less, with wheel speed, not engine speed.

    Work done to date:
    1) Inspected all wheel bearings. They are fine.
    2) Thought it might be the drive shaft u-joints or the centre bearing. Removed drive shaft. U-joints are fine and the centre bearing and rubber are fine. Giubo is just like new. Everything was tight and centre bearing was still preloaded. Just to be sure, we swapped the driveshaft out of our 1986 coupe into the 1987 and the sound was still there.
    3) Thought it could be the differential pinion bearing. So removed the 2.93 differential and installed our extra 3.73 Differential. And the sound is still there.
    4) Checked clearance between engine/driveline and the car's body and its all good.
    5) Checked the Condor engine mounts and tranny mounts and the are all good.

    Just wondering if anyone has experienced anything similar??

    I appreciate any input or advice you can offer.

    Thanks

    #2
    I have also experienced a similar issue with my swapped m30b35.
    Right around 2500 rpm when not pressing the gas, letting the car slow down on its own, it will make a thumping sound around the center console/ ebrake area.

    Its weird because the issue actually stopped for about 500 miles and now returned.

    I haven't had a chance to check the center support bearing, but I thought it would be strange to go away and then come back.

    Interesting to see what other people have experienced.

    Comment


      #3
      Any issues like that have been a weak CSB and/or driveshaft with sticking joints in my experience.
      Never argue with stupid people, they will drag you down to their level and beat you with experience. -Mark Twain

      Comment


        #4
        i just had a thump but under heavy load in all gears, obviously guibo. Funny thing was that it looked completely fine on one side but on the transmission side it had small cracks around the bolt sleeves. Your situation(s) are a lot stranger than mine though. Good luck, subscribing to this thread to see what others say.
        sigpic

        Comment


          #5
          Thanks for all of your responses. I appreciate all your input.

          Thanks glnr13. With all the switching of driveshafts and differentials, I didn't switch out the giubo - how dumb:(

          I'll try that next and I'll let you know if anything changes.

          Have a great day!

          Comment


            #6
            Originally posted by 325Contrails View Post
            Thanks for all of your responses. I appreciate all your input.

            Thanks glnr13. With all the switching of driveshafts and differentials, I didn't switch out the giubo - how dumb:(

            I'll try that next and I'll let you know if anything changes.

            Have a great day!
            Just wanted to note your correct spelling of the word "giubo". Thank you.
            Originally posted by Andy.B
            Whenever I am about to make a particularly questionable decision regarding a worryingly cheap diy solution, I just ask myself, "What would Ether-D do?"
            1987 325iS m30b34 Muscle car (Engine electrical phase)
            ~~~~~~~~~~
            I was born on 3/25…
            ~~~~~~~~~~

            Comment


              #7
              Thumping in Center Console - M30B35 swapped into E30

              Update: So have now replaced giubo and center bearing with new. Replaced output shafts. and still have the noise.
              Drained transmission fluid and replaced it with Redline (as someone suggested this might help if it is the getrag rattle LOL, but what the hell I am desperate:) The thumping got worse and there was a good size build up of metal shavings on the magnetic drain plug. So I think my tranny is shot:(

              Anybody know where I can find a Getrag 260/6???

              Comment


                #8
                Ouch - after swapping out all those parts, shame it's the transmission.
                My e30: OEM+ with M30B35

                Comment


                  #9
                  Thumping in Center Console - M30B35 swapped into E30

                  So while hunting for a the elusive replacement 260, we decided to pull the tranny anyway.
                  What we found were score marks on 3 of the 8 raised nubbies on the inside of the bell housing and burnish marks on the outside edge of the clutch pressure plate.
                  So we now think it might be that the Dual Mass (DM) that is starting to go or is out of wack.

                  So now also hunting for a single mass flywheel to see if the DM is our culprit. Fingers crossed

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                  Comment


                    #10
                    Not the Dual mass Flywheel.... Problem solved!

                    Well, it turns out that the thumping noise was not the flywheel.
                    After replacing the original flywheel, the thumping was still there.

                    So after another long hunt, we finally located a tranny out of a 1987 e28 in Ontario. Had it shipped here. Replaced all of the seals and in the process of reinstalling, we discovered the cause of our noise.

                    We couldn't believe what we found.

                    It turns out, the Sachs Clutch Kit we purchased (NIB), at the time of the original build, had the wrong size pilot bearing inside. They gave us a 15X32X10 pilot bearing instead of the needed 12X32X10.

                    At the time, we didn't think to dry fit the bearing with the transmissions input shaft. Why would we? The bearing's outer diameter fit perfectly in the engine and when we connected the tranny to the engine, we obviously didn't have a problem getting the input shaft inside. (Stupid us. We assumed/trusted Sachs to have the correct parts in it's clutch kits.)

                    So after 18 months, with no support for the tranny's input shaft from the pilot bearing, the tranny's input shaft bearing began to go bad, causing our noise.

                    So, with my son home for Christmas break, we picked up the correct Pilot Bearing ($16) and got the car back together and she runs perfectly. The tranny is silent and shifts smoothly.

                    What a headache, not to mention the cost and frustration, all because we trusted a manufacture and didn't dry fit parts before they were installed.

                    Just happy to have the the car back on the road.

                    P.S. Next project - tackle rebuilding the original Getrag 260/6 this summer when my son gets home from school:)

                    Comment


                      #11
                      Nice!
                      Originally posted by Andy.B
                      Whenever I am about to make a particularly questionable decision regarding a worryingly cheap diy solution, I just ask myself, "What would Ether-D do?"
                      1987 325iS m30b34 Muscle car (Engine electrical phase)
                      ~~~~~~~~~~
                      I was born on 3/25…
                      ~~~~~~~~~~

                      Comment

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