Nasty Sound, Not the usual clunking.. Options

[CrazyJ]

Guys,

Last two mornings in a row, turned out my street and start getting up to 60mph.

After 30mph a loud knocking/vibrating sound starts and gets louder the faster you go.

At first it was that loud I thought it was the engine, but as i slow down to 25-30 mph the sound stopped and the engine was revving fine.

I think it was coming from the back right of the car. Someone has suggested rear caliper sticking?

I know its not the common bushes problem because I have that too, but this is REALLY REALLY loud.

Once I slowed down to about 25-30 after about 100-200 metres its fine and doesn't do it again.

It also doesn't do it on the way home (start off in a 30 zone for a good couple of miles) so warming it up seems to stop it...

Any ideas?