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Driveshaft vibration starting @ ~75mph (long post)

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    tomstin I plan on updating all on here with any of my findings as this forum and many others have been helpful for me on figuring some of these things out.

    twright I'm not very concerned on the .004" as that's literally a sheet of paper and highest number after checking the mid/low/high diameters where the bolt holes are. Plus it bolts to the rubber flex disc which probably won't even have those tolerances itself. Yes, the driveshaft does fit snuggly on the end of the output, it does have a new (and greased) bushing and I could feel the slight friction of it just taking off the driveshaft last night. I think at this point I might put it back together, and just try forcing the driveshaft forwards as much as possible before tightening the center slider bolt. For some reason when I did this with more force than normal last time it seemed to help a bit. After that I think I will go ahead and order some new tires as the ones on the car are older all seasons that are ever so slightly out of balance and down to ~%30 tread. I was planning on the tires anyway because the current ones have some minor cracking and would also perform hideously at a track day.

    Maybe there is some weird harmonics with the slight out of balance tire issue because it feels like the vibration with no wheels on the car and suspension loaded at speeds over 80mph from the other night seemed to be half of what it was with the wheels on actually driving those speeds?


      I wouldn't be stressing about those numbers. I also wouldn't necessarily be stressing about the angle of the shaft, remember that light-medium duty trucks (not the 4x4 things that your pretend rednecks drive) use multi piece driveshafts with uni joints at large angles, and they don't vibrate either.

      I assume you tighten the centre nut after the ends of the shaft are tight and the CSB is preloaded?


      (clicky on piccy to get to thread)


        While you have the tires off, put the bare wheels on the balance machine and spin them. Any runout past about .5 millimeter will cause the vibration you're seeing.


          So I was putting the car back together and noticed I have almost .020" of play on one of the planes the rear u joint to the diff! The other plane on the cap 90degrees is fine with only a few thousandths play. One thing to note on this current driveshaft, the shop did not rebuild the u joints because because I was reusing the one that they (same shop) rebuilt ago 5 years under the previous owner, however I told them to do what was needed and was originally quoted for a full rebuild which was okay by me. I figure either the shop didn't check this or, or its something new caused from the vibration, however I find the latter highly unlikely as I have only driven ~200 miles or so on this driveshaft and kept speed under 70mph for most of the driving, most of which were driving back and forth to the shop. I will be calling the driveshaft shop Monday when they open, will keep you all posted when/if I get this resolved with the shop. This seems like a never ending saga, however I have no idea how I missed this before.


            econti I totally agree, I am not. And yes, that is the procedure I follow when installing the driveshaft. Now given the play in the driveshaft I have my fingers crossed that this was causing the issue.

            twright I will try to check the wheel runout too, as I could see it being a potential contributor to things. Will check before putting it back together next round. But It will probably be a couple weeks for me getting the tires, planning on visiting family in the midwest in early to mid October first.


              Hey all, so I spoke with the shop Monday morning and they were totally cool about it and agreed there should not be any play and told me to bring the driveshaft over and they would take care of it. So this afternoon I was able to stop by, they re-staked the axis of the u joint with play and re-balanced the driveshaft. I installed it tonight and it's fixed! The car drives perfect with no vibrations or anything, such a great feeling to not have to continually check all those things and having a BMW capable of more than highway speeds haha.

              Maybe I just had very bad luck with the first few driveshafts? I didn't actually really change much of anything or how I installed any of them. Oh well

              Anyway, thanks to all on here for your help and insight on this.



                Great! Thanks for the followup.

                It just goes to show how really small things can make a difference. (And harder to find when youi have a problem.)