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Thread: Thud/clunk from drivline-rear end

  1. #1

    Thud/clunk from drivline-rear end

    Hey all,

    Iíve been recently troubleshooting a thud coming from my driveline/rear end, when I first purchased the car I double checked the vehicle for subframe cracks even though PO had recent inspection by dealership, couldnít identify any via visual inspection so decided to tackle the differential bushings. I replaced all 3, job only slightly annoying, correct tools and watching youtube DIY videos are a must. Anyway put the car back together and still have the mysterious thud sound. It happens exclusively when disengaging the clutch when changing gear. Its not completely constant, usually more prevalent at lower RPMs.
    Iíve done a bunch of reading on some of the culprits, and am going to check the subframe mounting points again tomorrow but if I still cant see any cracks would a thud sound be possible if no visible cracks (aware there could be small ones I cant see unless I drop rear end). Read about CSB and Guibo on the driveshaft but that seems to be more of vibration/whining issue no? When I was doing the bushing job examined the rear sway bar end links and bushings and seemed fine as well, but could these come into play? Any chance the differential could have some type of wear on its splines that would cause this sound?
    Also will mention engine and transmission mounts have been replaced by me and I believe the clutch+flywheel(130k) are original.

    Thanks ahead time and sorry for the word vomit just wanted to try add as much context as possible.

  2. #2
    Join Date
    Jun 2012
    Location
    Socal
    Posts
    1,511
    Have you looked at the rear shock mounts? That would also create the same sound you're describing as well.

  3. #3
    have not, know the shocks/stuts have been replaced, ~40k on them right now. I’ll add it to my list of things to check tomorrow.

  4. #4
    Join Date
    Dec 2019
    Location
    Raleigh, NC
    Posts
    588
    I have the exact same clunk. I have new diff bushings and all new suspension. The only thing I haven't done yet are subframe bushings. Those are the most likely culprit, as old bushings will allow the entire subframe to move around drastically when drivetrain loads change (like letting go of the clutch) and hit other parts of the car as seen here:

    330i Base | Mysticblau | Slicktop | 6MT

  5. #5
    Join Date
    Mar 2011
    Location
    Independence KY
    Posts
    2,541
    rear subframe bushings I would suspect, if not, check the drivetrain/guibo/etc.
    2005 BMW 330i ZHP - BMWP brakes/intake/strut bar/shifter, Coby wraps interior, BBS CHs, Eagle Eye LED tails, LED fog lights, GC coilovers, Sprint Booster/sport button mod, 4.5 LCM w/ programming, Xtrons 9inch HU, BSW stg1, dynamat, M3 sedan dead pedal, oCarbon CF interior trim, CF seat backs, 2x2 CF MTECH2 diffuser, CF cabin filter cover



  6. #6
    Join Date
    Nov 2014
    Location
    Portland, OR
    Posts
    9,944
    Could it also be the driveshaft guibo/flexdisc (26117511454) or the center support bearing (26127501257)?

  7. #7
    I just checked shock mounts does appear like they are ready to be replaced. Its possible it could be either flex disc or center support bearing but I also don't really experience any prolonged vibration after initial thud. As it relates to subframe bushings if one is bad, am I’m potentially damaging mounting points driving the car?

  8. #8
    Join Date
    Mar 2011
    Location
    Independence KY
    Posts
    2,541
    I wouldn't be driving around beating on the car. normal cruising would be fine I would assume, but the sooner you replace them the better. if you are going to do all the subframe bushings, might as well do RSMs and other associated rear bushings/mounts. kind of a "while you are in there" type of thing.
    2005 BMW 330i ZHP - BMWP brakes/intake/strut bar/shifter, Coby wraps interior, BBS CHs, Eagle Eye LED tails, LED fog lights, GC coilovers, Sprint Booster/sport button mod, 4.5 LCM w/ programming, Xtrons 9inch HU, BSW stg1, dynamat, M3 sedan dead pedal, oCarbon CF interior trim, CF seat backs, 2x2 CF MTECH2 diffuser, CF cabin filter cover



  9. #9
    Also how do you guys post pictures on here, doesnít let me attach photos from my phone, even when I changed the format. Iím going to change RSM first, the metal appears to have separated from the rubber. I was planning on replacing subframe bushings+ reinforcing at some point, and while I feel comfortable dropping the rear end dont have any welding experience and would feel like a waste not installing some reinforcement plates, especially since they arenít all that expensive, has anyone went with the epoxy method?

  10. #10
    Join Date
    Mar 2011
    Location
    Independence KY
    Posts
    2,541
    if you plan on keeping the car for a while, this is just my opinion, but don't cut the corners. find a shop that can do the reinforcement welding for you.

    "set it and forget it"
    2005 BMW 330i ZHP - BMWP brakes/intake/strut bar/shifter, Coby wraps interior, BBS CHs, Eagle Eye LED tails, LED fog lights, GC coilovers, Sprint Booster/sport button mod, 4.5 LCM w/ programming, Xtrons 9inch HU, BSW stg1, dynamat, M3 sedan dead pedal, oCarbon CF interior trim, CF seat backs, 2x2 CF MTECH2 diffuser, CF cabin filter cover



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