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Motorway speed (and a bit...) vibration patch. Any ideas?

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    Motorway speed (and a bit...) vibration patch. Any ideas?

    Hello one and all. Time to tap into the Forum's combined intelligence and knowledge - which I know adds up to a brain the size of a planet! At somewhere around the 75 mph mark my Stag goes through a vibration patch. Purely in the interests of mechanical science, officer, I happen to know that it clears around 80 mph. It is particularly noticeable on deceleration, quite a judder and then clears at around 70 again. I've had the wheels balanced and there's no detectable difference. It feels like it's coming from the rear drive assembly somewhere. As far as I know the original drive-shafts are fitted. All rear suspension seems fine, has been polybushed at some point. I've had the car just over a year, I'm really pleased with it, and have quite good history but not complete.

    Whilst I don't make a habit of driving at illegal speeds, it is a symptom I'd like to get diagnosed and take it from there. Any ideas, tests, etc would be much appreciated. Many thanks.

    Paul
    Mk 2 1975 TV8 Mimosa

    #2
    hi paul you say you have had the wheels balanced does that include the rear wheels

    Comment


      #3
      Originally posted by stagling View Post
      hi paul you say you have had the wheels balanced does that include the rear wheels
      If you have no front wheel wobble at speed try those wheels on the rear and the rear on the front this should tell you if they are balanced, check with the tyre place that they balance the wheels on the stud holes not the centre hole as modern cars, they will look at you as you have two heads until you explain as they are mostly young and not seen these wheels before, this helped mine, but still not perfect, but work in progress, just rotated my prop 180 deg's yet to try.
      "The UK,s 2nd Most Easterly Stag" Quad Exhaust- ZF 4 Speed BOX

      Comment


        #4
        I had a similar vibration patch on my V8 Toledo, but that was at 60- 65mph. The problem was the propshaft, but I would check the quill shaft bearing as I believe this can cause similar problems.

        Neil
        Neil
        TV8, efi, fast road cams and home built manifolds. 246bhp 220lbft torque

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          #5
          I did have similar once, and finally, when it got really bad, I found a propshaft UJ had gone.
          '72 Manual O/d Saffron Yellow

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            #6
            +1 on Propshaft and / or Quill shaft Bearing.
            TV8, LPG, EEWP, HiD's, ZF 4, 15" Minilites, SS Bumpers & Exhaust, BMW Servo & Master, Rilsan.

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              #7
              Mines exactly the same. I probably have one of the Rimmers dodgy drive shafts. It is a CV jointed affair made for the SD1 Rover. I understand RB were modifying these to suit the Stag? Mines not modified but I do have extension pieces to take up the extra length required for the different engine and box combination.

              Comment


                #8
                Thanks everyone for your replies - greatly appreciated. The prop-shaft and/or universal joint clearly emerge as the prime suspects and figure with the type of vibration. I'll investigate it further from here.

                Regarding the point about wheel balancing, I do know about the not-perfectly-centred alloy casting issue and consequent problem with current wheel-balance methods. And yes, the Kwik-Fits wouldn't know about a stud tool method if you wasted time asking. That said, mine seem to balance OK so I can only conclude that the holes are centred accurately.

                Happy autumn driving (rutting??!!)

                Paul
                Mk 2 1975 TV8 Mimosa

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                  #9
                  I had exactly the same, thought it was the prop shaft, it turned out to be the Diff nose extension, had a new reinforced one fitted last year at the same time as having the rear suspension rebuilt by Favershams, totally gone now. I went through the whole rebalancing of wheels twice by different 'wheel experts' as well which failed to resolve the problem. Also discovered a dodgy front drag strut mounting that needed welding earlier this year that resolved a front wheel vibration.
                  Steve
                  1977 TV8 Russet Brown BW65 Auto 10CR and RBRR finisher

                  Comment


                    #10
                    That's exactly the same on mine except my vibration kicks in around 60 mph officer. Another job on the list for Paul.

                    Comment


                      #11
                      Originally posted by Paul Kelley View Post
                      Thanks everyone for your replies - greatly appreciated. The prop-shaft and/or universal joint clearly emerge as the prime suspects and figure with the type of vibration. I'll investigate it further from here.

                      Regarding the point about wheel balancing, I do know about the not-perfectly-centred alloy casting issue and consequent problem with current wheel-balance methods. And yes, the Kwik-Fits wouldn't know about a stud tool method if you wasted time asking. That said, mine seem to balance OK so I can only conclude that the holes are centred accurately.

                      Happy autumn driving (rutting??!!)

                      Paul
                      The cast ally wheels do not have concentric centres,so they have to be centreless balanced,ie bolted to the balancing machine.

                      Comment


                        #12
                        Originally posted by MandM View Post
                        If you have no front wheel wobble at speed try those wheels on the rear and the rear on the front this should tell you if they are balanced, check with the tyre place that they balance the wheels on the stud holes not the centre hole as modern cars, they will look at you as you have two heads until you explain as they are mostly young and not seen these wheels before, this helped mine, but still not perfect, but work in progress, just rotated my prop 180 deg's yet to try.
                        Just been for a 65mile run along to Minsmere, Dunwich, Southwold and Oulton broad, on the A12 at 59mph (Officer) vibration seems to have all but gone, after rotating my prop 180 deg's, Having previously replaced all the U/J's on the drive train, fitted modified nose housing on diff with SKF bearing, new bearings in my diff and backlash reduced, wheels balanced x 2, and fitting grease nipples to drive shafts. Think getting the prop balanced will do the rest, What do you think?, also poly bushes on the rear to do.
                        "The UK,s 2nd Most Easterly Stag" Quad Exhaust- ZF 4 Speed BOX

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