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  1. #1
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    Question Thump on "up"shifts from rear after Wavetrac LSD install?

    I'm experiencing a thump from the rear since I got the stock open diff replaced with a Wavetrac LSD. The thump happens strictly on upshifts only. There's no other noises whatsoever. The thump sounds like something hitting the floor in the trunk and it happens on any "up"shift ONLY AS THE SHIFTER IS BEING MOVED INTO GEAR. So, nothing to do with the clutch engagement/disengagement. I can press down on the clutch (disengage it) and while the car is coasting down say 50-60km/hr I can just move the shifter through the gears and on any "up"shift (neutral to 1st, 1st to 2nd, 2nd to 4th....NOT on downshifts) it'll thump in the rear...

    There's ZERO noises once the car's already IN gear no matter how you drive it. Car's a 2008 E90 335i 6MT. Since the LSD's been installed I also installed a new 6 puck ceramic clutch and single mass flywheel, the same clunk is still there.

    UPDATE: issue was related to damaged rear halfshafts and binding CV joints on them...after breaking one of them, got them remanufactured/upgraded by DSS and all vibrations/issues are GONE! Click here to enlarge glad its none of the issues I thought it was originally especially not my lightweight flywheel...i love that thing Click here to enlarge
    Last edited by dzenno@PTF; 11-01-2010 at 11:52 AM.
    Click here to enlarge

  2. #2
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    BMW's usually have a clunk in the LSD's which is a trademark. It isn't anything really to worry about and I'm not exactly sure what causes the clunk but every BMW I have had with an LSD has had it.

    This is an aftermarket unit though so just kind of strange but not abnormal at all. You will get used to it.

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    I'm not sure if it is normal w/ the wavetrac - i'm sure we've got a few members on here with it installed.

    What RPMs are you experiencing this at or would you say all RPMs - I know you mentioned it was only on upshifts.

  4. #4
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    Update? Heard you took it in but the thump is still there.

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    tranny shop said they couldn't do anything about the thump...they dealt with the gear whine (backlash was setup a bit loose)...i can eliminate or almost eliminate the thump 2 ways:

    1) speed up and while RPMs are still rising press the clutch and shift "up"
    2) not press down on the clutch pedal all the way down...if I press the clutch pedal just so that it disengages the clutch the upshift won't cause a thump

    I've got it boiled down to one of the following (will require inspection):

    1) rear diff mounts/bushings (from what I've read on other forums this had the highest number of occurances)
    2) rear subframe mounts/bushings (unlikely as the car would produce a thump on accel/decel on/off throttle, but possible)
    3) tranny mounts/bushings
    4) guibo and/or driveshaft center support bearing/bushing (unlikely as the car would vibrate under acceleration, I have none, but possible)
    Click here to enlarge

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    Click here to enlarge Originally Posted by dzenno Click here to enlarge
    tranny shop said they couldn't do anything about the thump
    I see. I think you will have to get used to it, I don't believe it can be eliminated and only happens in certain shifting situations as you said. Good luck, keep us updated.

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    Got under the car and checked it..with the car's rear up on a ramp, handbrake on and 1st gear engaged, I grabbed the rear nut where the driveshaft connects to the diff and I could twist/rotate it about 1cm each way..is this normal? Should there be any play here? Also halfshafts have back and forth play of about 1cm (in/out of boots) but no rotational play here..
    Click here to enlarge

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    Click here to enlarge Originally Posted by dzenno Click here to enlarge
    Got under the car and checked it..with the car's rear up on a ramp, handbrake on and 1st gear engaged, I grabbed the rear nut where the driveshaft connects to the diff and I could twist/rotate it about 1cm each way..is this normal? Should there be any play here? Also halfshafts have back and forth play of about 1cm (in/out of boots) but no rotational play here..
    The slightly play for the halfshafts is normal.

    Regarding the nut, that I do not know.

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    Along with UUC tranny mounts/bushings I've now put an order through for M3 rear subframe bushings, m3 rear control arms and diff carrier bushings...hopefully thump will be gone along with a lot firmer and stable/predictable rear end...
    Click here to enlarge

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    Click here to enlarge Originally Posted by dzenno Click here to enlarge
    Along with UUC tranny mounts/bushings I've now put an order through for M3 rear subframe bushings, m3 rear control arms and diff carrier bushings...hopefully thump will be gone along with a lot firmer and stable/predictable rear end...
    You are really trying hard Click here to enlarge I hope that helps as you don't seem to like it at all but I would not be surprised if it was still there when you shift a certain way...

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    Ok, so Click here to enlarge like FBIS said, i ain't going down silently with this thump and I AM swinging both hands until I'm satisfied that this thump must be there Click here to enlarge

    Just checked the Bentley manual for "allowable play" (play limits) in the front and rear driveshaft and here is what it says:

    2006-2009 3 Series Bentley Service Manual (Section: Driveshafts 260, 3-5)
    ======================================
    Front Driveshaft Service
    - Universal Joint Play, Max allowable = 0.15mm (0.006in)

    Rear Driveshaft Service
    - Universal Joint Play, Max allowable = 0.15mm (0.006in)
    - Driveshaft flange wear limits
    - Runout at transfer case output flange (max.allowable) = Axial play: 0.10mm (0.004in), Radial play: 0.07mm (0.003in)
    - Rear diff input flange radial play (measured at driveshaft center lip) = 0.07mm (0.003in)

    ======================================


    I'm very surprised by the max allowable play tolerances indicated. They're VERY VERY tight/small. If you take a look at post #69 above I grabbed at the flange nut and collar with my hand while the car was on ramps, in gear and with the handbrake on, and it would twist about 1cm (1000mm or about 0.4in) so about 100x more play than I should have....hmmmm.....

    Questions -
    1) Any idea how to tighten this slack at the flange bolt? I see Bentley manual says torque is 75Nm (55ft-lb)
    2) What/where is the driveshaft center lip? Is that at the center bearing somewhere?
    Click here to enlarge

  12. #12
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    Good luck, seems you are determined.

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    Just went for another look at the driveshaft...the radial play at the driveshaft I mention above is only present in neutral (clutch disengaged)...when the car is in gear and the clutch is engaged there's zero play anywhere...

    Does anyone know how much play they have in the driveshafts when in neutral/clutch disengaged?
    Click here to enlarge

  14. #14
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    Are you thinking the thump is due to the driveshaft moving once going out of netural?

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    Not sure but there's definitely slack there...i wish someone else with no thumps checks play on their car's driveshaft when in neutral (clutch has no effect here)...

    what baffles me is why the thump sound itself is minimized when upshifting with the clutch not all the way down...it still does it but its less...

    on top of all this, I've read tons of threads ppl reporting thumps with their Wavetracs and Quaife's and LSDs in general...but there are some, like former boosted, that has ZERO noise...if one car can have completely noiseless operation wouldn't another car be able to do the same?
    Click here to enlarge

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    Click here to enlarge Originally Posted by dzenno Click here to enlarge
    on top of all this, I've read tons of threads ppl reporting thumps with their Wavetracs and Quaife's and LSDs in general...but there are some, like former boosted, that has ZERO noise...if one car can have completely noiseless operation wouldn't another car be able to do the same?
    Logically, yes, but does he really have thumpless operation? Maybe he isn't as sensitive to it as you are?

    Like I said, the thump is common with LSD BMW's, I don't know why.

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    I talked with Fred Su at Evolution Racewerks about issues with the wavetrac. He hasn't heard of any, just speculates that if people are having some, it wasn't shimmed the right way. Good luck man! I must say that I was going to go with quaife after reading your threads on all the forums. However, I think I'm gonna let Fred do the Wavetrac after all. It won't be for another two weeks or so. I'll be sure to let you know how it goes for me.

  18. #18
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    Good luck man...hopefully it turns out zero thump noise for you if that's really possible...

    Fred's pointing at shims meaning he's talking about pinion preload...when the shop did my diff they didn't touch it so preload stayed the same AFAIK...
    Click here to enlarge

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    1 out of 1 members liked this post. Yes Reputation No
    Here's a clip of driveshaft play. In neutral, handbrake on...notice how much the driveshaft moves and that the halfshafts also move as a result but much much less..think its this slack in the driveshaft banging around making the thump?

    P.S. Excuse the Bon Jovi action on the radio Click here to enlarge

    Click here to enlarge

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    Hehe man, I'm really liking this thump detective work so far.

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    Hahaha thump detective
    Click here to enlarge

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    Sorry if this has already been posted, but, has anyone else with the wavetrac and 6mt also had this issue? Sounds like you are really getting after it. Are you able to refund your money in the worst case scenario? Has wavetrac offered to switch out the LSD, or, provided you a list of likely culprits given that they "should" be the experts? Just curious, and hoping for the best for your car.

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    Just as many ppl on the boards reported having any type of an LSD installed in their 335s, so far, I found only ONE that doesn't have the upshift thumps (former boosted)...I've contacted him to double check on this as well as on the driveshaft play part of it...

    I have contacted Wavetrac and they indicated a possible backlash issue but this was dealt with according to the tranny shop where I got it installed...as well as pinion bearing preload...

    I'm going for an inspection to an indy shop soon just didn't have time last week from work...i'll try to see if I can get another tranny-only shop to have a look at the in/around the diff and see if the above are setup correctly...wavetrac said that backlash should be 0.0035''-0.0045'' which is VERY tight...
    Click here to enlarge

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    i dont have the bump you're referring to. i have an quaife LSD tho, are you referring to only wavetrac users? everyone has issues? if so thats a faulty product. ive had my quaife LSD for almost 2 years now, i have never heard a bump or noise from it, i have never broken a half shaft but have snapped camber links on road courses. the bump can be fixd, but you're looking in the wrong places, what you're doing is trying to mask the sound instead of resolving it. unfortunately i think the problem is with the LSD unit itself. i would consider selling and trying a new company.
    Click here to enlarge
    2007 335i Coupe
    Mods: Check the Garage

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    Click here to enlarge Originally Posted by dzenno Click here to enlarge
    Just as many ppl on the boards reported having any type of an LSD installed in their 335s, so far, I found only ONE that doesn't have the upshift thumps (former boosted)...I've contacted him to double check on this as well as on the driveshaft play part of it...
    Good idea. The reality is most will have it and not even notice it.

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