Hi all,

I've got a Bailey Morris two-piece propshaft on my Fireblade car and recently I've been getting a vibration through the drivetrain when I 'let off' the throttle or when I am just on part throttle when at motorway crusing speeds (for example).

When I reapply the throttle the vibration goes away.

I've had a look inside the centre tunnel to check that everything is bolted down, and the only thing that I can see is that there is a fair amount (20mm in all directions) of movement of the centre UJ inside the central support housing...

I know that BECs have quite 'noisy' drivetrains, but the amount of movement of the centre UJ of the propshaft seems a little bit concerning...

Has anyone got any experiences/advice with regards the movement of the propshaft ?

TIA

Matthew

I believe chatter between the dogs in the gearbox. This only happens under very low loads. As you said it goes away when you accelerate, this is because you are applying a load to the dogs which is keeping them constantly in contact.

You may also notice if you lift off fully, the chatter disapears. This is because you are loading the other side of the dogs.

I know its annoying but I dont think it does any damage to the gears as there very little force involved in the impacts. My car does this and I know of several BIG bikes that do it.

I don't think there is anything whrong with your prop.

Hope this helps.
Carnut

[Edited on 5/7/05 by carnut]

Just noticed what you said about the movement in the centre bearing. Sounds like this may be the cause.

it will depend on the amount of play in your centre bearing..

mine is rock solid and i only can move it when using the car...

by hand maybe one mm

its the standard sierra Bearing..

Tkc

Thanks for the swift replies !!!!

The movement of the propshaft on my car is much much more than 1mm... and I can easily move it around 'by hand'...

How is the central UJ supported? Is it just by a rubber 'bush' or is there something more substantial ??

for want of a better word there is a crude bearing on the short part of the prop (just in front of the UJ) this in turn is supported by the rubber donut which in turn is incased in the metal supporting bracket
tony

The earlier transit centre bearing does seem to have a fiar bit of movement in the rubber, I can try in the morning but I wouldnt be suprised if its around 10-20mm movement on mine too.

As carnut mentions, you do get a clatter at neutral throttle where the gears arent under load, but its not really noticable as a vibration. Also check your prop flange bolt hasnt come loose and also your diff flange doesnt have any movement in it from a knackered bearing. Ive had both of these happen to me and they both caused vibration in the driveline, although probably on throttle as well as off.

quote:

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Originally posted by ChrisGamlin
The earlier transit centre bearing does seem to have a fiar bit of movement in the rubber, I can try in the morning but I wouldnt be suprised if its around 10-20mm movement on mine too.

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OK, thanks for all the replies so far. So it sounds that the movement of the propshaft is nothing out of the ordinary...

I've owned the car from new, but have never thought about lubricating the central rubber support 'donut' ..

Is this something that I should start doing ?

I've now had a further good look around the propshaft mounting points (front and rear) and nothing seems out of place/loose.

The differential (freelander) was also securely mounted in position.

Should I now turn my attention the gearbox end of things.............

???