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Can a diff create a vibration at low speeds?

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    Can a diff create a vibration at low speeds?

    Hi all

    I am trying to help someone who has an annoying vibration drone when accelerating and its around 25mph
    The car is fitted with the ZF box but the problem has been there since ownership in the 80's
    The prop was replaced when box was fitted and its a solid prop and again have ruled this out as problem was there before.fitting
    Being that it's around town speeds, it's alway there and is there from cold or hot.
    The car has done thousands of miles so ruling out viscous which seems to be ok etc
    Its had new tyres
    Rear U/j's seem fine too
    You can't feel it through the steering wheel

    The only thing that has been there since day one is the diff which has a slight wine too

    My question is, can a diff cause a vibration on acceleration at slow speeds of around 25-30mph?

    It feels like an harmonic drone when speed is building up

    Any experiences appreciated as he is desperate to solve the issue.

    Thanks
    Andrew
    Yellow Rules OK

    #2
    Which car is it out of. Bmw or Jag????

    Comment


      #3
      ZF gearbox he has is the Jag box but ruling that out as the problem was there when the BW65 was fitted.
      Diff is the standard 3.71 unit
      Cheers
      Andrew
      Yellow Rules OK

      Comment


        #4
        wouldn't have thought it's the diff as a low speed vibration would indicate a shaft imbalance has it been run with the back end in the air and the front chocked? this may show where the problem lies.
        I would go for the prop shaft first, try putting 2 jubilee clips round it with the screws together to create an imbalance then have a play with them to see if movement makes an improvement

        Comment


          #5
          Any thing touching body ? Gearbox cross member rubbing on body weak gearbox mounts. Have you tried rotating the torque converter around by one bolt. Rover had a problem with vibration with the zf they had to balance the flex plate with drilling flex plate and fitting weights to it.

          Cheers Glenn
          ​​​​​
          ​​​​​​

          ​​​

          Comment


            #6
            Thanks Phil and Glen
            Have been under car and cannot see anything touching such as exhaust through cross members etc and front cross member bushes replaced with superflex ones and made no difference.
            Had driveshafts out and all U/J's seem ok and regreased and splines greased
            Suspecting prop balance but would be surprised if out as it came new with the ZF box but considering this option.
            Tried my wheels on the car too to rule out possible flat spots on tyres.

            I think I need to have it up on stands as suggested and run it up and bit by bit remove shafts etc and see if it goes away to ID the part that made a difference

            Thanks all
            Andrew
            Yellow Rules OK

            Comment


              #7
              Andrew. The same vibration I tried to identify on a ESM? If it is happening at speeds as low as 25mpg, I doubt if it is propshaft related, and certainly won't be driveshafts,. You have specified MPH rather than RPM. Is it also engine speed related? You describe the noise as a "Drone" that builds up with speed. Could it perhaps be a wheel bearing?
              Mike.

              Comment


                #8
                Andrew,

                Check the front wheel bearings, even if they have recently been replaced. I consider myself au fait with bearing noises but had never heard anything like it, I seriously thought the gearbox or diff were about to fall out. The noise didn’t change whether turning left or right, so I was certain it wasn’t a wheel bearing!

                Eventually, I had a friend drive the car and listen to the noise, whilst travelling as a passenger, and I could sense/feel a roughness on the nearside front, my friend said he also thought it was a wheel bearing, so I stripped and replaced the front nearside wheel bearing, although it was less than 2-3 months old. The bearing was absolutely boll”*#%ed and it completely cured the problem, once it was replaced by a decent Timken bearing set. I did the other side just in case!

                I wouldn’t have believed how it transmitted through the car - cheap fix for once! Give it a try.

                ian F

                Comment


                  #9
                  I would not rule out the viscous fan coupling. Only when I changed mine (after it failed) did I realise it had been causing my driveline vibration all along.

                  Header tanks - you can't beat a bit of bling.

                  Comment


                    #10
                    to answer you question directly, Yes. But theres loads of other parts that do the same. If the diff isnt set up right or worn then can cause all sort of mischief.

                    Comment


                      #11
                      Originally posted by Ian F View Post
                      Andrew,

                      Check the front wheel bearings, even if they have recently been replaced. I consider myself au fait with bearing noises but had never heard anything like it, I seriously thought the gearbox or diff were about to fall out. The noise didn’t change whether turning left or right, so I was certain it wasn’t a wheel bearing!

                      Eventually, I had a friend drive the car and listen to the noise, whilst travelling as a passenger, and I could sense/feel a roughness on the nearside front, my friend said he also thought it was a wheel bearing, so I stripped and replaced the front nearside wheel bearing, although it was less than 2-3 months old. The bearing was absolutely boll”*#%ed and it completely cured the problem, once it was replaced by a decent Timken bearing set. I did the other side just in case!

                      I wouldn’t have believed how it transmitted through the car - cheap fix for once! Give it a try.

                      ian F
                      I also had exactly the same experience when I first got my Stag, in fact it was doing it when I bought it which helped keep the price down. I was convinced it was the diff. Sounded like it was from the back half of the car and again didn't vary when cornering. Found it when I got the car home and just started checking everything from front to back. I took the front hubs off to repack the bearings with greese and found they were both dry and and to use Ians words "boll”*#%ed". Replaced both sides and almost total silence.

                      So definitely worth a check, the clue to me is the fact you describe it as a vibration/ drone.

                      Roger
                      White TV8 BW35 no mods and now a Dolly Sprint to keep it company
                      So many cars, so little time!

                      Comment


                        #12
                        Hi Mike, Ian Wilf, Bullstarz and Roger,

                        It isn't my car Mike and mine is as far as I concerned, sorted now after change exhaust boxes and getting prop re balanced and changed the spark plugs as one was playing up

                        It’s Dad's Stag and he has had this issue as said since 1983 so can rule out such a lot such as viscous which is new anyway. In addition, the gearbox being converted to a ZF unit can rule out prop and the box.

                        The bearings are a good point raised as although it can go through an MOT, would it show up but then again, after all these years a bearing should get worse.

                        I mention the diff as it’s the only original part left

                        I think the only way is to run it up with stands under trailing arms and see if it can replicated when in gear. I can then disconnect a driveshaft at a time and see if it makes any difference.

                        I do take on board about it being a slim chance of being the diff at slow speed but he has a small wine and I think he is looking for an excuse to spend money on it LOL

                        Thanks all
                        Andrew
                        Yellow Rules OK

                        Comment


                          #13
                          Well, what a days this has been.
                          Got the Stag up on axle stands under the rear trailing arms and run the gears up and at there was the issue. I have felt it at first hand now and it's a vibration not a harmonic drone. You could feel it through the drivers seat and steering wheel. Put the gearbox into park and there it was, still there so proves has nothing to do with transmission. I have now established that it's the engine and it's not smooth from idle and peaks at 1,100 revs and there after smooth as it should be.
                          Now, going back to basics and knowing this has been for many years, I'm thinking, lumenition which has been on the car since 83, or carb issue sucking air in, crank pulley, viscous is new, dizzy wear, leads are new and plugs OK.
                          You can see and feel engine shimmer when you Rev it up and let the revs drop back to idle

                          Any suggestions appreciated such as lumenition issue experiences or carb points other than dampers sticking and diaphragms.
                          Thanks
                          Andrew
                          Yellow Rules OK

                          Comment


                            #14
                            Does it sound like a miss-fire Andrew?
                            Glad you didn't order a new dif'f!'
                            Mike

                            Comment


                              #15
                              Hi Mike
                              Exhaust note is the same so not a misfire. He has now commented that t feels like holds back beyond 70mph
                              All good fun
                              Yellow Rules OK

                              Comment

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