Help - Metallic rattle - offside rear... Anyone else had same issue?

As I was driving today, I noticed a very significant "metallic clanging" from underneath the car when it was going over rough road. It sounds not so much like a rattle as two very loose bits of metal "clanging together".

By process of elimination, it only occurs when driving the rear right wheel over pot-hole type bumps.
I don't get the clanging from driving either front wheel or the left rear wheel over bumps or potholes, just the offside rear.

I've been all over the underside of the car, expecting to see maybe a tie-rod loose and banging against a suspension arm or a bush completely missing, but everything seems tight and without play.

I've jacked both offside wheels up in case it was a broken spring rattling, but no luck there either.

Thought maybe it was a bit of the metalliuc heat shield from around the exhaust rattling on a silencer, but again, no heat shield is loose and the exhaust mounts all seem OK.

I've even emptied the boot of all the spare wheel well stuff, just in case, but no. Its definately from outside the car...

The car drives fine, steers and brakes fine. Can't find anything mechanically untoward, whether the car is jacked up or "on the level".

Has anyone had anything similar or any ideas? (Its a 3 dr 2wd 2.0TDi Sline by the way...)

Had a service and cambelt change in March but can't see how that would cause anything like this...

Any thoughts or feedback gratefully received.

The answer became clear today.....



Putting the car on the drive, I realised that the offside rear was a bit lower than the nearside rear corner.

Measuring with a tape, it was 15mm lower than the other side....
I took the wheel off and spotted that the spring was broken.

Still didn't explain the clanging noise fully until I dropped the suspension arm to change the spring today and found a small piece (4cm long - the left piece in the picture) actually loose inside the suspension arm.

That's what was clanging around producing the loose metal on metal noise....

Pair of springs cost £110 from DMS. They said they were a modified part and the Audi tech they had spoken too really strongly recommended changing them as a pair....