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    Driveline shudder with new components

    Hello. Story and question is as follows.

    M20b23, manual conversion by yours truly using a g260 and all that jazz

    1yr - 20,000km ago i performed the following:

    -new clutch
    -machined flywheel
    -new gearbox mounts
    -engine mounts were ok at the time.
    -rubber thing between the gearbox and driveshaft looks pretty new. I didnt buy it but it looks id guess less than a year old. still very firm.


    Started to develop a driveline shudder at a specific rpm at around the 15,000km after above work mark. about 1500-2500rpm under acceleration, it would not shudder before this, it would not shudder after. it was progressively getting worse, but still driving fine.

    I figured it was the centre support bearing. I bought a new one without even checking the old one, an aftermarket one, i cant recall the brand. whatever the generic German brand.

    When i removed the old center support bearing, the bearing and rubber was still in what i would consider usable shape. the bearing was perfectly fine. If anything the rubber was stifffer than the rubber in the new bearing i had bought. If i had checked before buying a new one i wouldnt have bought a new one.

    Since i had it all appart i installed the new centre bearing and rubber anyway. Everything went fine and i put it all together.

    I marked the driveshaft before pulling it apart. it went back the same way as how i pulled it apart.

    Not it shudders worse!!

    Basically it shudders less overall but it shudders basically from about 1500-4000 or even 5000. not sure but it does go away at higher rpm. But its defiantly more than before. its a more high frequency shudder than before perhaps.

    Engine mounts gone maybe? its all that is left.

    Rear cradle bushes i've no idea....probably had it? can this cause this annoying vibration?

    also i know i keep mentioning rpms, but the vibration is definitely speed dependent not rpm dependent.

    Ideas k go!

    #2
    Worn out u-joints on the driveshaft can cause vibration.

    Comment


      #3
      Ok I am back with more data and still a vibration issue. Car doesn't get driven that much these days....and I work too much away.

      I took my driveshaft out a few weeks back and took it too a driveshaft shop. They said my uni joints were all in fine working order, they did balance the shaft as well. They said it was out of balance but unsure how much. I suspect it was put together wrong at some Stage. They welded on some weights and painted it black and said it was now in perfect working order.

      Driveshaft went back in on the weekend. My installation method was that i loosened the slip coupling. Bolted it to both the gbox, diff and the center bearing. Unsure if the slip coupling actually moved, but once it was all bolted in I did the slip coupling back up again.

      AND IT FRIGGEN STILL VIBRATES!

      I must admit it is considerably better, probably the best it has ever been, almost passable. But there is still a vibration between 2000-3000 rpm. I want zero vibration. Absolutely none.

      Should i try loosen the slip coupling again and see if maybe its the shaft length needs to be slightly shorter? Is there are proper procedure to setting the shaft length post installation?

      Starting to piss me off!

      Engine mounts aren't new, but they are pretty good condition. Certainly aren't broken. I had a look at the diff mount. Looks ok, its probably original but its not in pieces or anything. I do have a new one to go in, but the old one isn't catastrophically broken.

      Comment


        #4
        You're saying it vibrates at a specific rpm- but in just 1 gear, say, 4th?

        If you're getting consistent vibration at the same engine rpm in different gears,
        it's not the driveshaft...

        As to length, I have had good luck just loosening it, letting it slip to where
        there's no preload, then tightening it back up. On other cars, I've found that
        tension is better than compression- but just a little, like a mm or 2.

        hth
        t
        Last edited by TobyB; 06-18-2018, 09:05 AM. Reason: reading comprehension
        now, sometimes I just mess with people. It's more entertaining that way. george graves

        Comment


          #5
          It appears to be worse and most prominent in 2nd gear at the mentioned RPMs.

          I will have another go at loosening the slip and making some adjustments and experimenting. Googling around the internet it seems that it might make some difference.

          I might have a better look at those engine mounts...

          Comment


            #6
            A few thoughts, make sure the slip yoke nut and bushing are in good shape and torqued correctly. Did you pre-load the Center Support Bearing properly? How's the alignment of the entire system? I posted a DIY alignment method on the DIY section.

            2004 525i Manual - 1985 325E Coupe Manual

            Comment


              #7
              I spoke to the driveshaft guy about preloadong the bearing and he definately advised against it. Though i do see it mentioned in regards to bmws.

              What is the proper procedure for preloadong the bearing? And where does it come from? Bentley manual?

              I had never thought about checking the alignment. Who knows how far out mine is. Thanks for the write up. I'll get the string out.

              Comment


                #8
                Originally posted by e30davie View Post
                I spoke to the driveshaft guy about preloadong the bearing and he definately advised against it. Though i do see it mentioned in regards to bmws.

                What is the proper procedure for preloadong the bearing? And where does it come from? Bentley manual?

                I had never thought about checking the alignment. Who knows how far out mine is. Thanks for the write up. I'll get the string out.
                I'm pretty sure Bentley says to preload the bearing and it's SOP IME. I believe it's 1/4" forward but dont quote me. I just know you do it.

                There is also a side to side alignment but I can't say that either adjustment can cause vibration.
                Seat Shocks....I have passed the baton to John Christy from Ninestitch. Email John or Garrett at ninestitch1@gmail.com

                https://www.r3vlimited.com/board/sho...86#post4944786
                Alice the Time Capsule
                http://www.r3vlimited.com/board/showthread.php?t=360504
                87 Zinno Cabrio barn find 98k and still smells like a barn. Build thread http://www.r3vlimited.com/board/show...20#post3455220

                Comment


                  #9
                  Hmm cheers. Well not a big effort to try the preload thing as I left the exhaust shield off.. ill give it a go.

                  Comment


                    #10
                    Drive line vibration

                    Could your Guibo be bad. A bad Guibo will cause vibration

                    Comment


                      #11
                      Originally posted by beancent View Post
                      Could your Guibo be bad. A bad Guibo will cause vibration

                      Originally posted by e30davie View Post
                      -rubber thing between the gearbox and driveshaft looks pretty new. I didnt buy it but it looks id guess less than a year old. still very firm.

                      Comment


                        #12
                        The csb should be preloaded a little- 2mm forward? Seems like just a bit's enough.

                        The driveshaft itself is not supposed to be- but again, just a bit of tension
                        has been good to me.

                        If it does it at the same rpms in different gears, tho, it would seem to be engine, not driveshaft vibes...
                        had a pressure plate fail once, and it did what you're describing.

                        t
                        now, sometimes I just mess with people. It's more entertaining that way. george graves

                        Comment


                          #13
                          Ok so i actually dug out the bently last night, found a copy on my laptop. I thought it was at home. Its very clear about the pre-load of the centre support bearing. Couple of mm is all it says.

                          It also mentions seizing of joining spline on the shaft as a potential cause for vibrations. I assume if this is seized up it doesnt allow it to extend/retract if required during installation. it also only specifies 17nm to do it up, which is bugger all, so maybe its not supposed to be done up tight and is allowed to extend/retract during use.

                          They also mention the alignment of the drivetraie (as discussed above) very interesting stuff and it gives somewhere to measure the alignment, ill have to get a bit more serious it seems on the alignment side.

                          I had not considered the engine side of things being an issue as everything is new, however i guess even the harmonic ballancer might be stuffed causing this. Id better investigate all things. It better not be the clutch, I've taken that gearbox out far too many times already. Bloody stupid bell housing bolts.

                          Comment


                            #14
                            Right well, i put a bit of pre-load on the centre bearing, took hardly any effort at all, just loosend the bolts, pushed it forward a tad and tightened it back up.

                            Fixed 99% of the vibration. Unbelievable.

                            Comment


                              #15
                              Originally posted by e30davie View Post
                              Right well, i put a bit of pre-load on the centre bearing, took hardly any effort at all, just loosend the bolts, pushed it forward a tad and tightened it back up.

                              Fixed 99% of the vibration. Unbelievable.
                              Funny how the smallest of details can make you crazy but glad you've got it sorted
                              Seat Shocks....I have passed the baton to John Christy from Ninestitch. Email John or Garrett at ninestitch1@gmail.com

                              https://www.r3vlimited.com/board/sho...86#post4944786
                              Alice the Time Capsule
                              http://www.r3vlimited.com/board/showthread.php?t=360504
                              87 Zinno Cabrio barn find 98k and still smells like a barn. Build thread http://www.r3vlimited.com/board/show...20#post3455220

                              Comment

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