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Can a diff create a vibration at low speeds?

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  • Goldstar
    replied
    Originally posted by Timo View Post
    Hi Goldstar, was it obvious the viscous coupling was failing once it was removed?was there signs of movement. Mine appears ok when on the car but does spin too freely probably a full turn or more.
    also would a tight tappet give me the same symptoms even though a compression test was fine.
    Mine span like that plus there was a little front to back movement in the bearing. Like Dave said worth replacing if it spins more than a blade or 2.

    If you pm me an email address I can send you video that might help.

    Paul

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  • new to this
    replied
    Originally posted by Timo View Post
    Hi Goldstar, was it obvious the viscous coupling was failing once it was removed?was there signs of movement. Mine appears ok when on the car but does spin too freely probably a full turn or more.
    also would a tight tappet give me the same symptoms even though a compression test was fine.
    If your viscous coupling spins a full turn,when you spin it by hand, you need to replace it

    Dave

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  • Timo
    replied
    Hi Goldstar, was it obvious the viscous coupling was failing once it was removed?was there signs of movement. Mine appears ok when on the car but does spin too freely probably a full turn or more.
    also would a tight tappet give me the same symptoms even though a compression test was fine.

    Leave a comment:


  • Goldstar
    replied
    Timo have you checked the viscous coupling? That can cause a vibration before it starts howling and really failing

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  • Timo
    replied
    Hi Andrew, just wondered if you got to the bottom of the vibration issue only i seem to have a similar problem with mine as it seems to be the engine vibrating\shaking when going from tickover to about 1500 revs when stationary and i beleive this to be causing a low vibration when driven, mine also has lumenition.so far i have swapped the following with no effect, Lumenition module,coil,leads cap and rotor arm, complete carburettor,engine mounts. timing is also ok and my plugs are newish but will replace going forward and vacuum advance works.replies welcome

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  • wilf
    replied
    One you have eliminated fuel and spark you may well come back to my viscous coupling suggestion. I checked/replaced EVERYTHING else before I got there. Can't tell you how nice it is to have eradicated that vibration.

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  • Andrew S
    replied
    Originally posted by mole42 View Post
    I’ve had similar trouble with an old Lumenition Optronic system. Having recently fitted a new complete Optronic system the engine is as smooth as silk.
    Thanks

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  • mole42
    replied
    I’ve had similar trouble with an old Lumenition Optronic system. Having recently fitted a new complete Optronic system the engine is as smooth as silk.

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  • ASL1956
    replied
    Exactly the same thing!! At around 45mph there is this low frequency low drone at that seems to be coming from the rear-ish. Not noticeable at lower speeds so interested in some of the responses here. I think putting the car up on stands and running it through the gearbox (BW35 recently rebuilt) might be the way to go. Hate those noises that you have trouble describing and even more trouble tracking down. I only logged on to see if I should put pink or blue antifreeze in when I fit my Stagwebber header tank later this week along with replacing the almost rusted through heater return pipe. The trouble with this excellent forum is that you come on to look for one thing and then end up worrying about 20 others!!! Happy days

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  • mike@thenook
    replied
    Hmm....

    i reckon it’s a timing/advance issue maybe or fuel related...

    Ok, I know that’s not very specific but all I can come up with at mo’.......

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  • Alacrity
    replied
    Are you SURE you don't have engine/gearbox mounting issues (for the vibration not the holding back!)? Thats what it sounds like to me.

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  • 022Dave
    replied
    Originally posted by Andrew S View Post

    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
    Hello Andrew,

    Money spent on good wine is seldom wasted.

    However, I suggest that you start with the basics to save needless time & expense. Look at the dizzy, particularly the central shaft hole of the plates, around which they rotate. Make sure that they are clean & the bits which are supposed to move are lubricated (I use Molly grease), such as springs and weights, and check the vacuum advance capsule for operation. Also check the small conical screw that secures the vacuum rod for wear; I had one once that looked like it had had an unfortunate relationship with a hacksaw.

    Dave

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  • Andrew S
    replied
    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

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  • mike@thenook
    replied
    Does it sound like a miss-fire Andrew?
    Glad you didn't order a new dif'f!'

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  • Andrew S
    replied
    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

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