Technical Rear drums making intermittent dragging sound

I'm hoping you guys can help me diagnose an intermittent rubbing/dragging noise coming from my rear drum(s) on my '48 Cadillac. The sound is at repeating intervals, depending on the speed of the slowing car. This only occurs when I'm applying the brakes and is audible especially at low speed, and stops when the brake pedal is released. I have just replaced the shoes and wheel cylinders and have acceptable pressure at the pedal. I did not replace the springs as they looked to be in good order. When this first occurred, I raised the rear and rolled out the adjusters to the point where I could feel a tiny bit of drag to remove excess slack. Upon the next test drive the sound returned. Do you guys have any ideas? I have discs up front.

 

You need to pull the drum off and have a look inside. Chances are you’ll be able to see what is causing the noise.

 

Couple of things.

On and off and on and off rubbing that jives with the speed of the car suggests to me that maybe you didn't have the brake drums turned and they need to be because they're out of round.

Look to see if there's a small pebble or a small bit of hardware or something that got embedded in the brake shoe.

You might try simply braking in reverse before pulling it all apart. I've dislodged a stone that way. But I'd wanna to look-see.

Good luck.

 

Could also be the shoes are rubbing on the edge of the shoe and not the pad surface. If the retaining springs that hold the shoes tight against the backing plate were weak they might be allowing the shoes to rub.
As mentioned you just need to pull the drums and look for shiny spots where it shows rubbing.

 

Drum touching the backplate maybe

 

I will do all of the above. I wouldn't be surprised if the drum were out of round considering the state of many things with the car when I obtained it. Thank you sir!

 

I'll open them up and have a look around. I should replace the old retaining springs no matter what. Thank you sir.

 

Drums off, look for shiny spots and see if powdered metal is all over everything. Can you narrow it down to one side?

 

Since you are diving in, you should be able to find the issue.
Please realize that older stuff transmitted noise more, that the way brakes were serviced when the car was young is not normally done these days (shoe arcing), and the drum might be good, but the axle flange off a bit. You need to check all carefully.

 

Another often overlooked item is a bad rubber brake hose that stops brakes from releasing fully, leading to dragging brakes. I had that happen to my 51, checked everything brake wise (except the hose) and could not find anything wrong. Next drive, same problem. Replaced hose and zero issues since. Good luck!

 

Good point, thank you sir.

 

I can't be certain what side it is but I'll soon know when I get some time to pull the drums apart. Funny thing is that the rear wheels look great tucked up under the rear of the car when driving...however this makes puling the rear wheels a bit of a chore necessitating raising the car high from the frame so the suspension can hang down to provide enough room to remove.

 

Check the U joints.
Check the tires and inner fenders for any signs of rubbing.
Check the rear spring shackles and bushings.
When you get the brakes apart check the backing plates for grooves on the pads the shoes slide on.

Before you remove the tires....
Spin the rear wheels looking for a wobble or bent axle shaft.

 

Good call on the u-joint possibility. Some bad ones will chirp more in reverse.

 

Wheel bearings?

 

Shoes may have worn grooves into the backing plates and are hanging up, not releasing completely. I have had to braze up the six points of contact on the backing plates and file them down smooth.