I just changed the rear drum brakes, brake drum and hardware on my 2005 Chevy Equinox. When the brakes are applied at speeds over 10 MPH, the brake shoes are pulsating in and out creating a knocking noise. I replaced the retainer and return springs with new. Everything feels like a tight fit. I made sure the self adjuster was fully extended to the point the drums barely fit over the brakes. The old brakes did not have this problem. Not sure went wrong here??