[urq] Whining noise when cold

[James Howard]

For the last 6 months on&off, I've noticed a whining noise from under the 
car when moving off from cold.
The noise only occurs if the car has been parked for at least a couple of 
days. It sounds like it's coming from under the car somewhere around the 
gearbox/driveshaft/rear diff.
The pitch of the whine increases with road speed only and is not affected by 
engine speed, or coasting with foot on clutch or in neutral, or applying 
hand or foot brakes.
It generally lasts for up to 1 mile and then suddenly dissapears (with an 
obvious cut-off rather than fading out) - sometimes the increases in pitch 
occur in distinct "steps" - like a bus or electric train changing gear, but 
the steps are not related to gear change.

Any ideas?

Thanks,

Jim.