Rear Drum Fiasco

[cham]

I'll start by saying I was chasing issues with front wheel bearings and brakes for a while now until I made the realization the brake pulsation and oscillation noise was more than likely coming from the rear drums dragging intermittently.  The issue though gets more difficult as I've replaced everything drum related twice within the past month.  First time around I replaced the both rear drums, shoes, and hardware with AutoZone parts which ended up being quite expensive because of the drums.  I also replaced the wheel cylinders with NAPA Premium and bled the system.  Post-installation, having adjusted the self-adjuster as close as possible, there was still slight intermittent grabbing.  This of course got worse as time went on as the self-adjuster pushed the shoes further out eventually.

 

Finally decided to return all of the parts except the wheel cylinders.  Instead I ordered a kit this time from CARID "Power Stop 1-Click Drum Brake Kits KOE15300DK".  I kept the NAPA wheel cylinders though, I didn't want to have to deal with replacing them again.  I'll cut everything short but having finished the install, the same issue is happening again.  I had to make a slight modification to the self-adjuster linkage actuator part as the indentation cuts on the shoes that the linkage part rotates in were too thin compared to the thickness of that actuator part.  I doubt though this would be causing the issue, if anything the shoes would just be slightly out of adjustment and rubbing all of the time throughout the rotation of the wheel, not rubbing intermittently.

 

I got so angry with the whole thing I just dropped it off at the local shop I frequent; he gave it back saying nothing was wrong, they made a slight adjustment apparently.  Well having got it back I lifted the rear axle and its grabbing pretty fricking bad for both rear wheels, both intermittently during rotation.  I really am curious if anyone else has had this much trouble with the drums before?  I can't imagine going through this twice and having defective parts in both situations like an out of round drum or something of that nature.  I guess anything is possible, but I'm thinking there is something else going on.  Still though, not sure what that might be.  Hope someone might be able to help, let me know what you all think!

Edited January 3, 2021 by cham

[Slartibartfast]

I know your pain! I hate working on brakes. The rear hydraulic circuit on mine gave me a runaround for months and I'm still not sure what was wrong with it, and the local shops were about as useful as yours.

 

Vibration and grabbing makes me think the drums aren't concentric to the axles. Check that the drums fit snugly on the hubs (no slop between the drum and hub that would let the drum sit off-center--I'd check this with the drum backwards to take the pads out of the equation) and that the end of the axle where the drum mates up is clean and flat (no chunk of dirt or rust or something making a drum sit cockeyed).

 

If you really wanted to rule out the drums, you could remove the pads and backing plates, mount the drums and wheels, and check the contact surface of the drums for runout with a dial indicator. This seems excessive, but so does most of what I tried when my brakes weren't working. I can't think of what else would be making the brakes vibrate, unless there's something very wrong with the ABS. I've heard of brakes grabbing if the leading and trailing shoes are mixed up, but not as a vibration, more as a "touch the brakes and they lock up" sort of deal.

[cham]

Glad I’m not the only one, this has been such a mess. To clarify I believe the oscillation to begin with happened because my front rotors were warped. They actually kept warping over and over again, after my shop replaced them for about the 4th time in a row for free I just about gave up as they weren’t worried about the source of the issue.

 

After replacing the front rotors myself I noticed there was a slight pulsation still and lifted the rear axle only to find the drums were grabbing intermittently so that’s why I am in this mess. I think if the rear is grabbing enough it can throw out the front and cause the front rotors to warp.

 

I know the shoes are on correctly as with what I mentioned earlier with the self adjuster linkage, it can only go on one way because of how it attaches to the trailing shoe. I’m fairly certain it’s the rear though because I can isolate it by pulling the handbrake while driving and get the exact same issue as when I put my foot on the brake. As far as what you say about the drum not being concentric, I’d think that’s totally possible. The holes in the drum for the wheel bolts seemed like they were big enough to allow play interestingly. I could just barely jiggle the drum when it was on and pressed firmly against the hub. My question would be, if I were to have someone apply the brake once they’re on and keep their foot on the brake through the process of mounting the wheel on, do you think this might eliminate the drum being off center of the hub?

 

 

Sent from my iPhone using Tapatalk

[FirstGenFreak]

I had a similar problem with my WD21 after doing all rear brakes (new drums, shoes, cylinders, handbrake cables) many moons ago. Didn't have the vibration but the grabbing. 

My conclusion was that the brake shoes aren't made to the same standard they used to be. Also make sure the leading edges of the shoes are chamfered.
I took mine to an old school brake shop  ( this is about 10 yr ago - they don't really exist here in Aus anymore). The guy there measured the drum, skimmed the surface and then radiussed the brake shoes to match the diameter of the drums (this optimizes the contact surfaces), plus put nice leading chamfers into the friction material. That fixed it in my case. 

 

Let us know how you go!