Can a longshaft be damaged beyond possible rebalancing?

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  • evilnickwong
    Grease Monkey
    • Aug 2007
    • 302
    #1

    Can a longshaft be damaged beyond possible rebalancing?

    Car:
    E30 318i M40B18 5spd

    History:
    Car used to occasionally have a horrendously loud clunk from the driveline tunnel under hard acceleration from standstill.

    Cause:
    Broken center bearing mount

    Action:
    Replace center bearing mount + guibo

    Result:
    No more klunking, but new vibration felt at around the 60-75kmh range in 3rd and 4th gears.

    New Actions:
    Sent the longshaft for rebalancing. Vibrations less, but still apparent.
    Installed a longshaft from another similar 318i. No more vibrations.

    ***

    So, since using the longshaft from another car cured the problem, that means the longshaft definitely appears to be the issue.
    My question is:
    1) Did driving around with the broken center mount previously damage the original longshaft beyond repair?
    2) Is it possible the place that did the longshaft balancing screwed up and it can actually still be rebalanced?
    3) When I had the center bearing first replaced, the longshaft was disassembled and the place I did it at did indeed mark the two sides with tipex. Is it possible they screwed up on the tipex?
    Tags: None
    • jlevie
      R3V OG
      • Nov 2006
      • 13530
      #2
      The center support bearing failed because the u-joints in the drive shaft were binding. That is why you still had vibration after replacing the CSB and why the vibration went away when you replaced the drive shaft. Any time the rubber mount of a CSB fails, both the CSB and drive shaft must be replaced.
      The car makes it possible, but the driver makes it happen.
      Jim Levie, Huntsville, AL

        Comment

        • evilnickwong
          Grease Monkey
          • Aug 2007
          • 302
          #3
          OK, understood that, but then if the driveshaft was the problem all along, how come there was no vibration before changing the center support bearing? Only after?

            Comment

            • jlevie
              R3V OG
              • Nov 2006
              • 13530
              #4
              If the rubber mount of the CSB had failed and you applied a lot of torque to the drive shaft in the lowest gears you would have experienced vibration. Under light torque loads there was enough motion in the torn mount to absorb the movement of the drive shaft. But when the new CSB was installed with a good mount that resisted motion of the drive shaft, that motion became apparent.
              The car makes it possible, but the driver makes it happen.
              Jim Levie, Huntsville, AL

                Comment

                • evilnickwong
                  Grease Monkey
                  • Aug 2007
                  • 302
                  #5
                  I see, that makes sense. Thanks for the info, will update if I find out anything new about it once I've gotten the longshaft work completed. :D

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