driveshaft knocking?

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  • blitzkrieg59
    Member
    • Oct 2004
    • 88
    #1

    driveshaft knocking?

    '89 325i. I've got a knock coming from my rear-end under load. Goes away in neutral and with clutch pedal depressed.

    Just jacked the rear end up and inspected wheels for any play re: bad wheel bearing. They checked out fine.

    Also got under the car with it running and in gear re: bad half-shafts. Noise doesn't appear to be coming from the axles or diff.

    Curiously the knock is almost completely silent until someone, or something with significant heft, is sitting inside the car. Sounds to me like the knock is coming from the driveshaft area.

    I'm about to head outside for deeper inspection via removing the shields over the driveshaft. But does this sort of weirdness sound indicative of anything to you cats?
    "Have no small wrecks. If you are going to loop out and hit something, hit it hard." — H.S.T
    Tags: None
    • Maddog
      Advanced Member
      • Dec 2006
      • 111
      #2
      If the noise/vibration is when you start off, it could be the driveshaft's center bearing.

      Check you engine mount, too, but I it's most likely the center shaft bearing.

        Comment

        • blitzkrieg59
          Member
          • Oct 2004
          • 88
          #3
          Further but still limited inspection revealed that this washer-looking thing at the end of the driveshaft, before the rear u-joint is scraping against the driveshaft tunnel. I can feel it snagging there when rotating the driveshaft by hand. Can't hear any clunking coming from the u-joints. This makes me think center support bearing, or transmission mounts, or diff mount, or some combination of these.

          "Have no small wrecks. If you are going to loop out and hit something, hit it hard." — H.S.T

            Comment

            • Maddog
              Advanced Member
              • Dec 2006
              • 111
              #4
              The center bearing is mounted on rubber in the bracket. When the rubber tears or deteriotes, this is when you will experience the thumping noise during acceleration.

              You should replace your guibo and rebuild your shift links while you have the driveshaft out.

                Comment

                • blitzkrieg59
                  Member
                  • Oct 2004
                  • 88
                  #5
                  I found that the passenger side transmission mount sheered, leaving about quarter-inch of space between the two sides of what remains of that mount. New transmission and motor mounts ordered. Talking to a local chap about a rebuilt driveshaft with new CSB and guibo included. And already have all the shift linkage parts and a new Z4 shifter waiting to go in. :)
                  "Have no small wrecks. If you are going to loop out and hit something, hit it hard." — H.S.T

                    Comment

                    • izickc
                      Member
                      • Feb 2013
                      • 59
                      #6
                      Please post if it fixes the problem I have the same issue.

                      Sent from my SAMSUNG-SM-G870A using Tapatalk

                        Comment

                        • blitzkrieg59
                          Member
                          • Oct 2004
                          • 88
                          #7
                          Will do. I'm going to try replacing the motor/transmission mounts first.
                          "Have no small wrecks. If you are going to loop out and hit something, hit it hard." — H.S.T

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