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Dull Clunking Sounds when moving forward from a stop, under load.

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  • Dull Clunking Sounds when moving forward from a stop, under load.

    I have been experiencing clunking sounds when moving from a stop. It sounds like it's coming from the rear of the car but not 100%. After the car starts moving, say 10mph, the sound is no longer there. Only when starting from a stop under load. Just had it on the lift, where a couple of British car mechanics had a look and could not find an issue but could duplicate the sound when driving. Very frustrating! Again nothing wrong once the car begins to speed up. My only though at this point is it possible the rear axels might be causing this? Lack of grease??? Had rebuilt then just a few years ago. Any ideas?

    Randy
    1972 TR6 Jasmine Yellow CC79030U
    Purchased in 1973, 3rd owner
    Restored 2009

  • #2
    A couple of things come to mind. A loose lever shock mounting will give a clunking sound and did the British car mechanics check the differential mounts carefully?
    Almost every TR6, still on the road, has had to have the mounts re-welded, with strengthening plates.
    CF1634U+O Pimento/Chestnut
    2nd owner, since 1975
    Now in Fair Oaks, CA

    Comment


    • #3
      Yeah occasionally it could be the axles being worn. Most time it’s the right(passengers) side front diff mount. Usually cracks side to side and it’s usually due to worn bushes. You can’t see it unless you get a mirror up there OR drop the diff. You’d need a strong light & mirror. You might see the crack, you might not. And as baws said, they all do it
      So much rust, so little time

      Comment


      • #4
        They all clunk- that is until the right front differential mount is repaired.
        You can't see the mount location where it rips apart the metal, unless the differential is removed.

        Of course, your cars noise could be a U-joint or worn axle splines or lever shock mount (as baws noted) or loose lug nuts or a rear hub about to break off the axle at speed or gears inside the diff broken up or a loose exhaust system hanger or rubbing.
        But, it is probably the right-front diff mount that has torn apart the steel cross member.

        Click image for larger version  Name:	DSCF1150 (9).JPG Views:	2 Size:	378.4 KB ID:	526125

        In this photo you can see a right-front diff mount that has been poorly repaired.
        Left side is an original that is okay.
        The reason it is so difficult to see from below is that the crack is usually at the base of the mount- on the cross member- right around the pin.

        TRF sells the custom cut mount, the pin, a base reinforcement plate, a center plate with the pin hole and side reinforcement plates.
        A welder will need the car up on a lift with exhaust & diff removed, to do a quality repair.
        Last edited by SapphireBlue72; 09-03-2019, 07:25 PM.
        Walt
        CC80954U '72 TR6 original condition/sold 16.500.
        poolboy rebuilt the Z-S Carbs. Philstr6 rebuilt both rear hubs.

        Comment


        • #5
          I'm still quite ignorant about the TR6. But I had this exact issue in my Ford truck. I would listen to everybody else before you listen to me! But for my part it turned out to be loose bushings on my sway bar. It would clunk just like that whenever I took a turn or accelerated from stop. The sway bar would flex and do its job but the bushings were loose and I would get that clunking sound. Might check that out as well.
          Last edited by Shadetree; 09-03-2019, 05:19 PM.
          New to the British auto world.
          No qualifications - old school shadetree mechanic...just enough knowledge to be dangerous!
          1973 TR6, ZS carbs, Pertronix ignition (for now)
          1973 Ford Bronco, 302 V8
          1952 Ford 8N tractor
          ...they keep me busy!

          Comment


          • #6
            Yes, bushings, good point- something that I forgot to mention.
            One member here had The Clunk and replaced the bushings that support the diff on its (4) pins.
            That ended his clunk, IIRC.
            Walt
            CC80954U '72 TR6 original condition/sold 16.500.
            poolboy rebuilt the Z-S Carbs. Philstr6 rebuilt both rear hubs.

            Comment


            • #7
              Thanks all. I am pretty sure it is not the differential mounts. BTW when I take off from a start it’s not just one clunk, but a number of them from different areas in the rear and quite noticeable. At first I thought it was a body shifting issue but have ruled that out. Right now I’m contemplating taking off the rear wheels to make sure the hubs are properly tightened.
              1972 TR6 Jasmine Yellow CC79030U
              Purchased in 1973, 3rd owner
              Restored 2009

              Comment


              • #8
                To test the hubs, raise the rear wheels off the Earth.
                Grasp the tires at opposite sides at different angles & attempt to wiggle them.
                If there is any give, you have got a hub problem.

                You can not tighten the hubs, they must be rebuilt or replaced.
                The hubs do have a reputation for fragility on TR6's.
                The steel can crack and the hub & wheel can go rolling past you as you drive.

                Walt
                CC80954U '72 TR6 original condition/sold 16.500.
                poolboy rebuilt the Z-S Carbs. Philstr6 rebuilt both rear hubs.

                Comment


                • #9
                  My rear end clunk was a slightly loose shock mount bolt.
                  SR
                  73 TR6. HT/AC/OD
                  86 930
                  91 535i

                  Comment


                  • #10
                    Or u-joints...
                    '74 TR6 CF13007U aka "Mr. T"
                    Custom Blue (Delft-Like) and New Tan (Formerly Mallard and New Tan)
                    Points, Ballast Bypassed, Bosch Blue Coil, Moss Cobalt Wires, Champion RN12YC plugs.
                    Peaks and tweaks, but the spirit of Original
                    Redlines always.
                    My wife is the Driver, I'm just the Mechanic....

                    Comment


                    • #11
                      Originally posted by TRIFIK6 View Post
                      Thanks all. I am pretty sure it is not the differential mounts. BTW when I take off from a start it’s not just one clunk, but a number of them from different areas in the rear and quite noticeable. At first I thought it was a body shifting issue but have ruled that out. Right now I’m contemplating taking off the rear wheels to make sure the hubs are properly tightened.
                      Hearing more than one 'just one' clunk steers me away from the usual culprits like the diff mounts. Loose shock mount, maybe. Also check any place where the exhaust pipe can touch the frame as the rear end oscillates when first accelerating. Try banging up on the pipes or muffler with something like the heel of your hand?

                      Dick


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                      • SapphireBlue72
                        SapphireBlue72 commented
                        Editing a comment
                        Commonly where the pipes pass through the T-Shirt/crucifex area.

                    • #12
                      Randy
                      check your wire wheel to make sure they are tight and greased
                      Phil

                      Comment


                      • #13
                        Originally posted by TRIFIK6 View Post
                        Thanks all. I am pretty sure it is not the differential mounts. .....
                        Have your diff mounts been repaired and boxed in? If not, don't rule out a cracked mount. You can't see the cracks unless the diff has been removed and the mounts wire brushed..... and even then it can be tough to see a crack.... here's what mine looked like after they were cleaned up.


                        1975 Mimosa with a few upgrades/mods:
                        Patton TBI
                        HVDA Toyota 5 speed
                        Goodparts Nissan Diff
                        Goodparts CVJs
                        AAW Wire Harness
                        Miata Seats
                        Boyd Welding Custom 15 gallon aluminum gas tank

                        Comment


                        • #14
                          I have the car up on stands today to take a closer look. Phil I just took off the rear wire wheels and everything is fine with the adaptor and wire wheels. BTW I though the same thing. Give me a call Phil when you can. Question, is it possible the rear axels need to be greased again? Could they be a possible source? Something to think about. Or for that matter the drive shaft? I will report back later today after I review things. Walt, you have a point as well. The rear hubs could be an issue and I will check the play in them. I know there is a little play but not enough that I was concerned about it. Just to refresh everyone, the "Clunking" sound appears to come from where the axel and drive shafts are. Really hard to pinpoint when taking off and hard to tell when up on blocks. Really need to be able to check it under load. Appreciate everyone's though on this.
                          Randy
                          1972 TR6 Jasmine Yellow CC79030U
                          Purchased in 1973, 3rd owner
                          Restored 2009

                          Comment


                          • #15
                            While I didn't notice more than one clunk at a time under the conditions similar to your description, I found it was coming from the REAR differential mounts, where the inner metal sleeve had become "unbonded" from the surrounding rubber part of the mount...
                            If you have aftermarket, polyurethane mounts there wouldn't be a metal sleeve.
                            Driving a 1973 TR6
                            Doing ZS carb repairs
                            email kencorsaw"at"aol.com

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                            Dull Clunking Sounds when moving forward from a stop, under load.

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