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Trying to help a TR6 owner who has a vibration when driving especially in 3rd 4th gear.

No problem in 1st 2nd but when in 3rd it starts to build up.

Where to start looking any ideas ?    gearbox ?   prop shaft ?  wheels ?    nothing obvious when inspected.

Roy

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I had the same problem on my 3A and it was the propshaft . I removed it and had it balanced by a specialist who is based near Moss. They also stripped all the old paint and finished it with a new coat of black. I used new special bolts supplied by Moss and the vibration has gone away

If you need I can find the name and address later on.

Richard & B

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Quick test for prop shaft/drivetrain is to get up to vibration speed and knock the car into neutral, if it goes away or reduces dramatically it’s drivetrain and most likely prop shaft.

John

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1 hour ago, John Morrison said:

Quick test for prop shaft/drivetrain is to get up to vibration speed and knock the car into neutral, if it goes away or reduces dramatically it’s drivetrain and most likely prop shaft.

John

As the shaft and drive-train continue at the same relative rate of rotation as the wheels are turning, irrespective or not of whether the car is in neutral, then your suggestion is that that the vibration occurs because these components are lightly loaded (steady speed) ?

Pete

 

ps. I say 'relative rate' because the prop-shaft is of course turning almost x4 as fast due to the diffential's gearing.

 

 

Edited by Bfg
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Propshaft, diff, driveshafts wheels/tyres are road speed related.

Engine/GB are RPM related.

Loose bodywork

Is it from the front or back of car???

As the problem does not happen at low speed (1st & 2nd gear) then it sounds road speed related.

If it has come on suddenly check the tyres for bulges and excess wear.

If it has been growing check the UJ's

As suggest above - get to the speed that causes the vibration then drop into neutral.

Vibration gone - check engine mounts, exhaust touching body, Clutch not happy.

Vibration remains - check tyres, UJ's, Dampers

 

Roger

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Hi Pete,

vibrations due to imbalance are independent of the load (think of balancing a wheel).

Because of the much lower speed of the two drive shafts, compared to the prop-shaft, the prop shaft is more sensitive, as the imbalance force increases to the 2nd power with (rotational) speed.

Cheers,

Waldi

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1 hour ago, John Morrison said:

if it goes away or reduces dramatically it’s drivetrain and most likely prop shaft.

I’ve read this before and, don’t really understand the logic.

As Pete has just said, the propshaft is still turning as long as the rear wheels are turning, so I would guess if the prop was out of balance it would still vibrate.

I’m working on a wheel-balancing machine at the moment. It measures the out-of-balanceness of the wheel using a load cell connected to an amplifier connected to an Arduino microprocessor.

I spin the wheel up and get vibrations. When I remove the wheel spinning device I still get vibrations.

Charlie.

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Thanks Waldi,

I thought that to be generally true, and so in tracing vibration one can narrow things down by the vibration being linked to 1. engine revs, 2. drive (prop) shaft speeds, and then 3. wheel, hubs & bear bearing, as well as rear-axle or half-shaft speeds (3. as a result of the differential ratio after the drive/prop shaft).

However, I asked the question because I might envisage jointed parts like worn c.v. joints twisting sideways - when under load ..and that joint only 'straightening out' again under reverse load.   

 

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1 hour ago, Charlie D said:

 

I’ve read this before and, don’t really understand the logic.

As Pete has just said, the propshaft is still turning as long as the rear wheels are turning, so I would guess if the prop was out of balance it would still vibrate.

I’m working on a wheel-balancing machine at the moment. It measures the out-of-balanceness of the wheel using a load cell connected to an amplifier connected to an Arduino microprocessor.

I spin the wheel up and get vibrations. When I remove the wheel spinning device I still get vibrations.

Charlie.

+1

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You should be able to tell, by the frequency of the vibration, whether it is caused by out of balanced propshaft,(high frequency) or (more likely) out of balance wheel, or wheels. (much lower frequency)

It could even be out of balance brake drum. I recently balanced my drums, & was surprised how bad they were. Having done it, the vibration I was getting has gone.

Bob

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vibration on mine was a combination of every single possible source :)

- replaced and balanced tires, better but not quite good enough

- replaced prop shaft and moved to CV joins including new rear hubs, another improvement but still not perfect

- replaced front bearings made a small improvement

- replaced wheels - finally all perfect with no vibration at any speed!

good lucking tracking the source, may be coming from multiple places.

cheers,

Laurent

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On 7/20/2022 at 10:56 AM, Charlie D said:

 

I’ve read this before and, don’t really understand the logic.

As Pete has just said, the propshaft is still turning as long as the rear wheels are turning, so I would guess if the prop was out of balance it would still vibrate.

I’m working on a wheel-balancing machine at the moment. It measures the out-of-balanceness of the wheel using a load cell connected to an amplifier connected to an Arduino microprocessor.

I spin the wheel up and get vibrations. When I remove the wheel spinning device I still get vibrations.

Charlie.

Try it - works 

John

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37 minutes ago, John Morrison said:

Try it - works 

John,

Thinking about it a bit more in depth…

If, say, there was a lot of rotational play in a prop UJ, the flange could be in a slightly different position relative to the actual prop tube depending on whether it was being driven by the engine (Box in gear) or by the back wheels (Box in neutral) .

(Prop flange driving the prop tube as opposed to prop tube driving the prop flange)

That slight variation in flange/tube position may cause vibrations.

 

So yes, maybe I was wrong…..:(

 

Charlie.

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  • 4 weeks later...

Thanks all

once under the car checking uj's it was obvious.   one front bolt was missing from the shaft/gearbox end, had snapped off the grease nipple on its way out.

Roy

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It might sound stupid but when we were checking mine out for a similar issue we discovered that the propshaft was on back to front!. On checking it out there was wear on the splines and we replaced it with a good secondhand one from John Morrison's loft. Loads better now.

I've also bought a set of wire wheel balancing cones as no local tyre fitters had them (Cumbria). Turns out that they were miles out of balance despite having been recently 'balanced'.

Andy

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