Chattering/ knocking rear brake when brake is applied

Their should not be much play in the pad you may have a stuck piston of the caliper, have someone step on the beaks to see if then the break pad has presure on it fron the piston to see if it is moving.

I just had a stuck piston on the right front.  The car pulled considerably hard to the left, at the same time I also noticed a high pitch squeel while driving (no brakes applied), I decided to completely re-build the entire front end brake system including bearings, calipers, rotors and semi metalic pads.  Works great now. Another thing to check would be the parking brakes since it is the rear on yours, make sure they are not hanging up and the cable is free.

Thanks for the reply, I will take a better look tomorrow, will keep you posted.

You should not have play.  That is not normal.  Check springs and parking brake and brake shoe.

The calipers are only 1 year old. if i press the brake hard there is no chattering

What about the Parking Brake shoes and Hardware????

I will take a better look tomorrow.All four pistons seemed fine, just some play  side to side on outer brake pad. Maybe its not the pads?

Checked the pistons, they looked fine, took the pads out put the two back to back and noticed the outer one was slightly shorter in length. Switched the two pads back into the caliper and problem was solved. 

Thats the ticket !!!!