Propshaft vibration

[Gavin]

Looking in the Haynes manual one of the courses of prop shaft vibration is ' shaft refitted in wrong position' - now I know you would normally mark the shaft and gearbox flange but if you've replaced the gearbox how do you know what the right position is? The shaft def isn't bent or out of balance as it didn't vibrate before I changed the gearbox and it does now (above about 65 mph) so I suspect the shaft is out of center in relation to the gearbox output, how do you ensure its centered? Is it worth me undoing the propshaft and moving it round 90 degrees relative to the gearbox to try each position to see if that loses the imbalance?

Thanks Gavin

[Nick Moore]

The bolt pattern at each end isn't square, so you'll have to turn it 180 degrees. Did you replace the gearbox mounting as well? Herald family propshafts are notorious for balance problems, and an old, oily, spongey gearbox mount might have been absorbing the vibrations.

[C Mallock]

Whats the history of the gearbox?
Bearing breaking up on the output shaft maybe?

[JohnD]

As Nick says, the flanges at each end only allow two positions in which they can be bolted up, so that means four different set-ups.    If, IF, these allow an imbalance, then one should be awful, two so-so, and one perfect.   Mark both end-flanges and the gearbox and diff. flanges so that you can try the permutations.   But I agree that other causes are more likely.

The other way is to put two large Jubilee clips around the shaft, and use the screws as balance weights.  Start with them opposite each other and move one - only one - while you test the result by driving it.    VERY time consuming, but hey - don't you WANT to drive your Triumph?

John