8.8 disc brake "groaning"

[Shran]

Annoying new problem - I recently 8.8 swapped one of my trucks with an Explorer axle. All was fine for the first few drives around town, parked the truck in the garage for a couple weeks and now when I roll it back & forth by hand in neutral, or drive it back & forth slowly, I get a horrible low pitched groaning noise from the rear end. I have narrowed this down to something in the brakes - I had the rear end off the ground and it'll make the noise when I spin the tires. Removed driveshaft, same thing. Removed calipers & rotors, no noise. The driver's side parking brake shoes were way too loose so I adjusted them and it seems 95% better, nothing weird happened on my test drive, parked it in the shop again and the noise is back a few days later.

Any ideas? Literally everything in the rear brakes is new except the calipers. The backing plates and caliper brackets were sandblasted & painted, everything is nice and clean so I'm not dealing with rusty old junk here. I am leaning towards an adjustment issue with the parking brake shoes but it's sort of confusing that it went away and now it's come back.

 

[pjtoledo]

some rear axles have an anti-groan brace, maybe Mustangs?????
there are also vibration dampeners on some.
try new piston seals, at least they're cheap.

if you suspect the parking shoes, coat the "drum" with something like a magic marker to show contact spots.

spray some water on the disk to isolate the noise, one surface at a time.

 

[Ranger850]

If your pads are shiny, You can try scuffing the rotor AND pads with scotchbrite or almost ANY grit sandpaper. I have used the concrete floor to scuff pads before. IF it goeas away, then comes back in a few days or miles or whatever, you got bad rotors and they may need turning or replaced.

 

[sgtsandman]

My 2011 has a damper on the end of one of the two caliper bolts on each side. That did pretty well until I installed the heavy duty pads that don't have the ends chamfered. Like mentioned above, I believe some of the Explorer axles had a vibration damper on the pumpkin. I'm not sure if that was for the brakes or something else.

 

[Shran]

Think you guys are onto something regarding the pads, it did it again yesterday after sitting for a week. I notice if I apply the brakes just a tiny bit, the noise immediately stops.

I do have tapered pads. Pretty sure I ordered ceramic ones from centric but I don’t have the box or receipt.

I tried something last night, when I did brakes on my wife’s car recently the pads came with very specific bedding instructions (basically braking from 50mph down to 5 or so, 10-15 times, then let it cool.). I did that, started smelling brakes so I let them cool off and then drove it, noise gone… I’m pretty sure at this point that it is my pad/rotor combo at fault and the parking brake adjustment deal was just a coincidence.

 

[Ranger850]

I’m pretty sure at this point that it is my pad/rotor combo at fault and the parking brake adjustment deal was just a coincidence.

me too

 

[Shran]

Drove it to work this morning and it was fine. Fingers crossed I guess.

 

[dvdswan]

Silly statement, you did remove the protective coating on the rotors before installing everything, yes.

 

[Shran]

Yeah, I always hit them with brake cleaner before installation.

 

[Ranger850]

Propper break in is key when it comes to new or turned rotors and pads. It can also happen to drums and shoes. Bad tips on the lathe can add squeel or groan to an otherwise perfect rotor/drum