Tapping, knocking speed related

[DavetheBlade]

Evening all, I wonder if anyone can shed any light or have any thoughts on this. Set off from work tonight driving slowly across the car park and heard a flapping type of noise from the rear. The only way I can descibe it is if you whirled a wet towel against the floor (please feel free to get a towel and try this if so inclined) so initially thought something stuck to the tyre and carried on.
Still there so pulled over and took a look expecting to see something in the tyre or wrapped around a drive shaft or prop but nothing.
Continued home and as you do tried driving in different ways all the time analyising the noise. So above 30 can't hear it, may still be there though. Coasting down a hill can definitetly hear it, but as soon as I accelerate gently it goes away. Braking seems to make no difference nor hard acceleration. My only guess is bearings in the drive shaft, I've had this before on a different car but it was a very definite clacking noise at low speeds only. The noise I'm getting is much more muted so not sure if it's the same.
Any help greatly appreciated.

[Leslie]

There is a steady bearing made of rubber in the centre of the prop you might want to check may well be hidden from view on the x5 I don't know , it can knock against the aluminium housing if the rubber has failed , tends to only happen at low speeds and higher loads like going uphill .

[DavetheBlade]

Thanks for the response I will take a look and see if that might be the culprit.