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Driveshaft vibration starting @ ~75mph (long post)

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    Driveshaft vibration starting @ ~75mph (long post)

    So last year I picked up an 89 325i automatic and basically went through the whole car mechanically and suspension wise and swapped in a getrag 260. Anyway, before doing any of this work the car was basically 100% original except some Bilsteins and Eibach springs and although the rear subframe bushings were pretty well gone I could easily take the car up to 90+mph without any noticeable vibrations. However after my swap I noticed a very a vibration coming from mostly the rear of the car but also seat feeling as well, it is a very high frequency and not related to wheel balance as it didn't exist before and I rotated the wheels front to back with no changes. Additionally it is seems largely irrelevant to engine speed and being on/off the throttle. The vibration can be felt slightly at around 75mph and picks up a bit with more speed, however it never gets so bad I feel it will actually damage the car short of maybe less u joint life. That being said, my 226k mile old subaru with original driveline seems to feel silky smooth vibration-wise compared to my E30 at any speed over 75mph which was not the case before the swap. I've had 4 newly rebuilt driveshafts in the car now, largely with the same exact problem so given they are all from reputable companies I do believe it's an engine/driveline alignment issue.

    Below are the related driveline/suspension items I replaced all at the same time:

    HD rubber Engine mounts w/ aluminum cups
    HD rubber trans mounts w/ aluminum cups
    the car has the correct OEM 5 speed stamped steel crossmember
    garagistic 80a poly rear subframe and diff mounts (I had 2 other diffs in driveshaft #1, #2 , and #3 with rubber mounts, no change except for the speed vibration started, diffs were oem 4.10 open, 3.73 open, then finally 3.64 torsen now). The taller side is on top as per instructions
    guibo (Febi) was literally almost new so I reused it for the for first driveshaft, I replaced it anyway with a new Febi one with the 2nd driveshaft with no change
    new GKN CV axles - after driveshaft #1, made no difference but the old ones were starting to get bit of play anyway with 190k miles
    new wheel rear wheel bearings - after driveshaft #1, no difference but replaced because they're old

    Other notes: all driveshafts have the new nose bushing, grease, new CSB (none were cheap URO garbage). giubo is line up correct with arrows pointing at the flanges, all 6 bolts/nuts are the same, CSB was pre loaded as per the bentley manual in all installs, the first 2 driveshafts I tried rotating 180/90 degrees etc and nothing changed at all. Starting with the 3rd driveshaft I even got a laser to ensure the driveshaft was totally straight front to back, but main focus was the on both an up and down and left to right plane the front driveshaft is within .3 degrees of the engine/trans (digital angle finder, said to be accurate within .1 degrees or so). The engine, driveshaft sections and rear diff are no more than .5 degrees apart from one another (within bentley specs). Although I didn't check the first 3 driveshafts the max run out, on the 4th one I found after measuring in several spots of each section, run out was no more that .010" and nothing has any play which seemed okay to the shop and from my online searches.

    driveshaft #1 - reputable TX company, noticed vibration around 60mph

    driveshaft #2 - same company as above as above, switched to 3.73diff, speed jumped to closer to 70mph, then switched to 3.64 diff, maybe another mph or so more, driveshaft was returned as it was marginally better than the first vibration wise, they were cool about it since I am not close to TX to have them look at the car

    driveshaft #3 - from a local company (20 min drive), said they would be able to help me diagnose if not the driveshaft, installed it, was basically same or marginally better than the TX company, but when asked they said they won't do this diagnostic service for BMW contrary to what I was told when I purchased the driveshaft, however they did return it without issue.

    driveshaft #4 - I took my auto driveshaft to the company that rebuilt it as an auto under previous owner and they put a 5 speed section on the front and re-balanced, the auto driveshaft was almost brand new/freshly when I got the car. They said its probably not the driveshaft but alignment of it if it still vibrates after. I installed it and the vibration was slightly less but was starting to be noticeable at 75mph (before with the others it was 60-70ish depending what rear was with it, so this one was a bit smoother). I think they were all probably the same, its just I was super attentive to the driveshaft alignment because I had taken apart and double check so many things. I took it back to them to have them check the alignment and they said everything was good and nothing to adjust (focused on the front mostly where adjustment can easily be made, however they looked at it all supposedly) They were actually surprised how close I had gotten it myself. The owner recommended I try adjusting the pinion some to see if it helped but I didn't notice any changes (pinion down 2 degrees further using washers, I tried about 4 iterations to get this and none helped, some made it worse, especially at 2 degrees, but marginally so)

    At this point its okay enough as I can cruise at 80mph and not be too annoyed with just minimal vibration, but I still don't feel like this issue is resolved and even a very reputable shop couldn't diagnose it. I even spend $100 on this driveline vibration app and it flagged only one thing, driveshaft vibration lol. Does anybody have any idea what could be causing this vibration or any potential things to check? I have never spent so much time and money trying to diagnose something like this with essentially no results or without finding anything I did wrong, or part out of spec, etc. Feel free to ask for any further details on what I have attempted to explain above too.

    Thanks for reading, I feel like this is a novel at this point.

    EDIT: cleaned up a few typos
    Last edited by 84svoracer; 09-22-2021, 07:51 AM.

    #2
    Get the car on stands, have someone sit inside, and run it at the speed that it starts. Does it have a new flex disc? I have seen vibration from one of them, and also from the transmission output being slightly tweaked.
    I don't think that it's the alignment of the shaft.
    -edit- I also assume that you tightened the friction nut in the centre of the driveshaft real tight?
    sigpic

    (clicky on piccy to get to thread)

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      #3
      Make sure its the driveshaft.
      A good shop can analyze the vibration for you and tell you which frequency it is: wheels or driveshaft.

      Or, you can do it yourself: Get an App called Vibe for your hone and go for a drive. It will identify the frequency of the vibration, and with a little math, you can tell where its coming from.

      Comment


        #4
        econti yes, I reused the original flex disc, then even though it was basically new with no cracks, I replaced it with a new Febi/Bilstein flex disc. There was zero difference. I did tighten the friction nut, however not real tight, spec was 7 ft/lbs, granted I used a large slip joint pliers and am sure its much more than 7lbs, probably at least 2X that. Although I didn't directly check the output of the transmission, when measuring run out within 2 inches of it I didn't get any large values. Are you saying the actual output shaft itself or the 3 pong thing at the end of it?

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          #5
          twright Most driveshaft shops here won't touch BMWs and I can't imagine how much it would cost bring it to a BMW dealer, the one shop that did check was the one that built the shaft. That being said, the speed of the vibration is directly related to driveshaft speed, not wheel speed as per my differential switches above, additionally I tested this in my garage on jack stands without wheels (rear control arms holding weight in the rear @ ride height and get the same vibration. Just the feel of it the frequency seems much too high for wheels being out of balance. My last comments in my long post I did get that exact app and it said case 1, driveshaft. But after 4 new driveshafts it does basically the exact same thing, so I'm basically ruling out it being that out of balance/round. So it must be an angle of something or direct driveshaft connection (at least I think so)

          I think it has something to do with the guibo/ujoint angles. Maybe I will get a new output flange as per econti 's post because it is a used 260 (no output shaft play), but maybe the previous owner bumped/slightly bent the output flange?

          Comment


            #6
            Just get it up in the air and have a look. It should be very obvious what it is then. Yes the actual gearbox output was bent, only by a bee's dick but enough to vibrate. Was very annoying.
            sigpic

            (clicky on piccy to get to thread)

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              #7
              econti I will take a look and try to convince my wife to give the car gas to those speeds while its on jack stands and report back. Out of curiosity, did you have to swap out transmissions or was the output shaft repairable or fixable?

              Comment


                #8
                Just checked with the car on stands and suspension loaded. No noticeable driveshaft movement or vibrations from looking at it. There was a slight vibration feeling putting my hand on both the rear diff and rear of transmission case.

                I should note that the driveshaft vibration is relatively minor at this point, its not a strong "there's something seriously wrong with the car" kind of thing, even taking it up through 120mph (on stands jack stands). That being said, it's not what I would describe as super smooth driving at 85mph either if that makes sense.
                Last edited by 84svoracer; 09-22-2021, 06:27 PM. Reason: Added stuff

                Comment


                  #9
                  After reading all this the guy knows alot about cars and covered all possible causes, Since he developed the vib. after tranny swap then i would only suspect engine to transmission alignment i once had a vibration due to misalignment when suddenly deaccelerating from 5k rpm but mine was rpm related.

                  At the end try to swap another working tranny and see.

                  Comment


                    #10
                    Mount a dial indicator somewhere close to the rear diff and sweep the pads on the differential. Make sure that they are all in the same plane, within a few thousands of an inch. Do the same with the rear flange of the transmission.

                    These surfaces have to be square with the driveshaft.

                    Comment


                      #11
                      ADEN I wish I had another transmission, if you know of a cheap getrag 260 laying around in good shape let me know

                      twright, I'll check it out, I'm thinking the rear is probably fine, but am more suspect of the transmission. Will pull the driveshaft and check those after work and report back

                      Comment


                        #12
                        Very strange. Driveshafts don't actually have to be dead straight - as long as its balanced correctly and components in good condition it can be at angles and still be fine.
                        I'd experiment with spacing the trans up or down using washers on either side of the mounts, and also spacing the CSB down using washers, to see if that makes any difference. Good bit is its cheap and easy to do.
                        Other than that I'm largely out of ideas, and I've spent a lot of time diagnosing vibrations in my cars.
                        sigpic

                        (clicky on piccy to get to thread)

                        Comment


                          #13
                          I totally agree it's very strange, but much more frustrating. I measure the run out perpendicular to transmission/diff flange mounts and it varies .004" at most. I also checked the runout of the transmission output shaft and it was only .002", so I think I can safely cross those off the list as causing any issues. The only somewhat off thing I noticed is that my output flange has '265' stamped/cast on it. See the pic below. The raised center portion is still lower than the flex disc and I don't see how that would make any difference, but is this the correct part for a getrag 260 in this car? I know the trans is a later model 260 and not a 265, its not an removable bellhousing or anything and doesn't have the crank trigger mounting stuff like on the older ETAs.


                          Click image for larger version

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                          Additionally, I have messed around quite a bit shimming the transmission/rear diff mounts quite a bit to basically have 0 felt change in anything. The only thing that seemed to have helped a bit was pushing the driveshaft forward very hard before tightening the center locking thing for the driveshaft length.

                          Comment


                            #14
                            I hope you figure this out and please post your results. I've been fighting, what I believe is a drive line vibration, and can't seem to figure it out.
                            2004 525i Manual - 1985 325E Coupe Manual

                            Comment


                              #15
                              Originally posted by 84svoracer View Post
                              I totally agree it's very strange, but much more frustrating. I measure the run out perpendicular to transmission/diff flange mounts and it varies .004" at most. I also checked the runout of the transmission output shaft and it was only .002", so I think I can safely cross those off the list as causing any issues. The only somewhat off thing I noticed is that my output flange has '265' stamped/cast on it. See the pic below. The raised center portion is still lower than the flex disc and I don't see how that would make any difference, but is this the correct part for a getrag 260 in this car? I know the trans is a later model 260 and not a 265, its not an removable bellhousing or anything and doesn't have the crank trigger mounting stuff like on the older ETAs.


                              Click image for larger version

Name:	Output2.JPG
Views:	34
Size:	78.3 KB
ID:	10032046
                              Additionally, I have messed around quite a bit shimming the transmission/rear diff mounts quite a bit to basically have 0 felt change in anything. The only thing that seemed to have helped a bit was pushing the driveshaft forward very hard before tightening the center locking thing for the driveshaft length.
                              I'm not sure if .004" is close enough. I was hoping for .001-.002'. If it were my car, I would try to put a small shim or two on the offending pad and see it that helps.

                              Another thought: Does the end of your driveshaft fit snugly on the pilot of the transmission shaft?

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