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Rear-end vibration


David McHugh
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Hi All. Since I bought my Spitfire IV 74, I have had quite bad vibration at the rear-end and a slight clonking as I pull away. I did discover that the rear end of the prop shaft was not connected correctly (metal strips not even) I corrected this and removed a jubilee clip that had been placed around the rear of the prop shaft. I have checked all the universal joints for play, none found but I have replaced the radius arm bushes and there is no uneven ware on the tyres. There is some play on the off-side out-put shaft and the wheel bearings are all okay. I can't say that I have noticed any difference in the vibration on the overrun.

 

I really don't know what to do next, I would imagine removing the diff is not a particularly easy job so I thought perhaps changing the input/output bearings would be the next step? Are there any other things I can do without having to remove the diff from the car?

 

Your thoughts and ideas would be greatly appreciated

 

Kind regards David.

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yes i echo that 

 

diffs dont make vibrations as the previuos owner had added a jubilee clip to attempt a re balance its pointing to propshaft .

 

if removed make sure all the gearbox and diff couplings are filed flat ,no bruising to the faces  these must be 'flat' or coupling run out will make vibrations 

 

 check the UJ for lift and if OK  then its  search for a local proshaft repairer get the old one spun and checked ,

 

Pete

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One Jubilee clip can only make vibration worse, as the screw mechanism will be much heavier than the mass that is causing the imbalance.

 

First, check the front and rear flanges.    Each has four bolt holes, in two pairs, unequally distributed around the rim, so that the input and output flange pairs, front and back, can only be connected in two ways, not four if all the holes were symmetrical.     Thus, there are only four ways that the whole shaft can be bolted up.  One way is perfect, one gives dreadful vibration and the other two are so-so.     Carefully mark the flanges, so that you can undo them and reassemble each in the two possible ways and then try all four.  

 

Then return to the Jubilee clip, or clips, as you should fit TWO, with the screws diametrically opposite, so that they will have no effect on balance.   Then move one slightly and note the improvement, or not.   If it doesn't move it the other way.  If it does, continue to move it in the same direction until the vibration worsens again.   Again careful and detailed marking and notes will keep you organised.

 

Finally, or perhaps first as it is easiest, rear end on axle stand, start the engine and observe. NOT from under the car!  Do the wheels spin straight?  Is any vibration evident?  Repeat with wheels off to exclude wheel wobble.

 

You cannot complain about the first two options as they offer endless hours of essential test driving in your Triumph!

 

Good luck

John

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Strap drive props are notorious for problems.

And an out of balance prop again is a dreadful thing. If you can borrow a known good one it is really handy. If not a new one may be a wise investment. It really can transform the car. Either that or hours playing with jubille clips. And that DIY method does work, as long as you are methodical.

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http://www.canleyclassics.com/triumph-spitfire-mkiv/1500-propellor-shaft/

shows a strap drive and a CV prop.

Most (It seems) heralds had solid props with just a UJ at each end

again many Triumphs had a sliding spline joint

http://www.rimmerbros.co.uk/Item--i-GRID005726

 

Having the dsolid props can make life harder than it should be as there is no movement to get theprop in and out of the car, and the engine/box position must be perfect. Plus no allowance for a little flex in the chassis. I believe it makes the UJ's work hard!

 

The strap drive appears to be a cheap fix, but seems rather under-engineered. Sliding joints or CV's rather better.

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also some early had no restraint in the engine mounting rubbers and seem to rely on the strap drive using the diff to stop engine shifting on braking early had a also a cable tie bar from chassis to the rear engine plate to hold her in place

 

dont know if the two idea's were at all related but if you have flat/rectanglular  engine mounts , they will allow shift

 

if  they are the deep dovetail type they control engine position and I believe these best suit  the telescopic prop.

 

but must be fitted the correct side of the turret 

 

Pete

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Thanks guys, I am somewhat relieved that it is most likely the prop and not the differential. The reason I thought it might have something to do with the differentiial was the slight knocking sound I get when pulling away. The biggest problem I have is living on Portsea Island, I have to drive five miles to get to somewhere that I can drive fast enough to test any alterations that I make, I guess it's going to take a while. When I first looked at the strap drive, the straps were not put on evenly as well as having the jubilee clip, un fortunately I don't know if the straps were changed on purpose to try and rectify vibration, not that it really makes any difference since correcting the straps does not seem to of made any difference.

If I was to have the prop balanced or buy a balanced one, would it be a case of just fitting it once , or does it have to be tested and turned 90 degrees at a time until the drive is smooth?

 

Thanks again for all the comments which are most helpful as usual.

David...

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dont think triumph fitted things twice  

 

     it should be fit and forget , if rotating it 1/2 turn makes any changes it due to other things at gearbox or diff end having a flange problem

 

      over the years these get abused and damaged faces and burrs on holes etc  , get a good file and make them all flat , if there is any runout you need a dial indicator to measure it, easier to buy new couplings and replace if there's any doubt.

 

on any propshaft its important the joints are phased, its normal for the journals on the tube ends to be in line (including a telescope one) 

with multiple props some need to be out of phase with each other 

 

    why.. this is because the joint does not rotate in a circular motion due to the angles involved and if out of line the tube will be let say  if you replaced all the clock face numbers with a rotating tube  which also rotated around the clock face is what goes on under your floor,

 

 

Pete

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I have heard of a chap removing the straps and bolting the 2 bits together effectively making a solid prop. Apparently that worked, no idea if it would in your case but easy enough to try?

 

And as pete says, prop balance has nothing to do with how it is fitted in relation to other components. If it does have an effect, there are other issues to be dealt with!

 

I would not bother getting the strap prop rebalanced. For all the grief call Dave Mac propshafts and buy new. Really, a very good investment. (unless you can get a known good one secondhand, known being the important bit)

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  • 4 weeks later...

I thought the strap type prop was fitted to cure the vibrations?

If you want to try balancing the prop try Johns two opposing jubilee clips, easiest way is to  jack car up level, take rear wheels and brake drums off and place V section stands under the vertical links so the weight is on the suspension.

With the front on stands or ramps for stability you can run car in top without leaving the garage (leave door open though) vibration usually happens about 45mph and move clips as required.

Derek

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