strange noise

[gingimark]

I have an Audi a4 2.8 Quattro and brakes are hardly working.I am taking it in to be repaired next week,but wondered if anyone could help me out.The brakes have gradually been getting worse over the last few weeks.When i start the car and apply the brakes they seem ok.But after a while are very poor.Within the last few days there is a noise coming from the rear of the car when in motion,and gets faster as i accelerate.I was told that it could be the bearings but i jacked the car up and wheels are firm.I thought that it could be brake related??Also somebody mentioned that it could be the rear diff.As i am pretty clueless when it comes to the mechanical side of things i would appreciate any help.:confused:

[lonky]

are the rear brake pads worn out ?

Look at the rear disks and see if they are scored, that would be a good sign.

If pads down to metal braking would be bad, and only the front pads have wear sensors