Rear Drum Brake Woes

[the hammer]

So, I have a 2006 CC Z71 w/ rear drum brakes. I replaced the shoes with a set of Raybestos PG plus shoes and I put on new drums from raybestos (I needed new ones to paint them, old ones were rusted bad). Not only were the drums out of round brand new, but now I seem to still have some pedal pulsing when braking after turning the drums, and furthermore I now have a scratching noise when I brake. The catch is, the scratching noise happened before I changed the shoes and drums (thus it happened with the factory drum and shoes), and only happens when applying the brake and ist is not constant. The sound goes scratch...scratch...scratch... and is based on how fast the truck is going, so it is obviously related to brake bads/drums.

 

My questions are: 1. What is causing the scratching noise and 2. After turning the drums should they be out of round still?

 

Josh

[Havasubum]

I also have pulsating rear drum brakes on my 06 GMC Z71 4X4. I've already had the drums turned once and it still pulsates. I don't have a scratching noise though That's what happens when accountants build the trucks rather than engineers

[sillyazz]

Sounds more like the front rotors are warped .

[the hammer]

That would be the case had there been pulsing before I changed the drums/shoes, but it was smooth before. I changed because of the scratching and also so I could paint the new drums nicely.

[Zembonez]

That would be the case had there been pulsing before I changed the drums/shoes, but it was smooth before. I changed because of the scratching and also so I could paint the new drums nicely.

I don't know who made the drums you bought but a lot of them are cheap Chinese castings... even from reputable companies. I have seen some really bad "out of the box" drums and rotors. Perhaps you got a bad one. If it is a weak casting and is warping, it would also be possible for it to make the scratching sound on light braking.

[the hammer]

So, in regard to these shoes and drums I am at a loss. What would cause drums to scratch intermittently as the wheels rotate and as the brake pedal is applied; and the sound is like a screwdriver scraping over a wire brush, very loud and clicking-like? It wouldn't have anything to do with the rear differential would it? I mean, could that be some weird stretch of the cause?