REAR DISK BRAKES HUMMING

I put rear disks brakes on my 67 barracuda. I finaly got the chanc to put a few miles on it. When ever i come to a stop i have a load humming noise coming from the rear of the car. It onle=y does it when i push on the brake peddle. I got the brake kit from performance online. The set up design is from an 80s caddy w/ the E brake cable. Other than that they work great. Any ideas ?
Sounds like the same set up I used to sell. I was dealer for TSM. Sounds like rotor warped. Not sure what they use now but the last 2 kits I saved for personal use has FORD rotors machined for 8 3/4 Dana 60 fit.