Rear Disc conversion super noisy?

Before you do, remove the caliper and see if you've got any side (in and out) movement in the axle, the sound you're hearing could be the green bearings side loading. When you apply the brakes the piston pushes the disc, therefore the axle, out till it meets the outer pad (not much but it does). How old are the green bearings. This is why I like the Kelsey Hayes design on the front discs cuss that design squeezes the disc to stop.