New shoes, new drums. Aftermarket. I know... Shoes are the good ones with the standoffs pressed in already.
Put all new fluid in all brake lines.

Fronts are fine. I know this because the rears where full of gear oil and thus not working . So I had to redo everything.
Random gear oil left some places? Out of round drums?

Should I try to brake clean the crap out of the 2 yo oem shoes and reinstall? One old drum was out of round, its what did the seals in. All of the other seals died when the diff exploded, so it was time.

What says you?

 

Did it do it as soon as you re-assemble?
First, I would just open up and inspect. I used NAPA NON-premium brake shoes and cylinders and they're working well for me. If diff had exploded, double-check that axles are OK?

 

drums are warped. i just went through that. brand new drums, shoes, and hardware. warped right from the first mile. slapped on some slightly used oem drums and shoes, no more vibration.

 

Ask yourself how and why a circle might become an oval in a rotating assembly...

Check for out of round and run-out on drums and axels

 

To check for run-out, you'll need a tool like this:
https://www.aliexpress.com/item/4000022226634.html
https://www.aliexpress.com/item/33032998053.html

 

So I mount them both in a lathe on an old axle, check for roundness. Ok.
This was my first idea, but everything is fine unless they heat up under heavy braking. Which made we wonder why they would only be out of round under more than light braking.


I've never checked run out on axles. Hmmm. Off to google

 

Have one for my lathe. Think it will work ok if I just put the drum on "backwards"? Then I don't to build stuff.

 

I imagine if it's bad enough to destroy your brake piston seals you might even pick it out by eye.

But yes start with just the axel face and a visual. Clean flat and running true to the backing plate with no excessive play (bearing issues), studs not bend just a general " check everything ". Maybe need a washer stack, don't know if the lugnut is long enough, but yeah inside facing out should be close enough. Again you might need anything that accurate and can see it with eyeballs and maybe a decent ruler.

 

Didn't see the first half of that.
... Might be hard to tell the difference between heat expansion and just the feed back pulse you'd notice pressing hard on the pedal.

 

I just need to take them off and check. I'll report back.
First I'll bleed the brakes again and degrease the drums and pads and retry.