Rear drum brakes chirping?

The right rear brake on my van "chirps" when braking (kind of a chirpy, squeaky noise). Lately I have been having problems with that same wheel engaging first under hard braking. In fact, it locks up completely before full pedal on the brake. I pulled the wheel and drum, replaced the wheel cylinder that seemed to be leaky and rebled all the lines and the problem still exists. Its really aggrivating and I can't pin it down. Any ideas?

The linings may be contaminated with brake fluid and should be replaced,

I remember having this same problem with a car I had 30+ years ago. Seems like it was a wheel seal, but it could have been a leaking wheel cylinder. I just can't remember.

You need to first be sure you've isolated the correct problem, but chester is right. Once the linings have been contaminated they need to be replaced or you'll never be totally rid of this issue. But find the culprit first, or you'll have to replace them twice.

Is it adjusted correctly? Is the anti chirping spring missing off the drum? Did you inspect the other side too? Maybe its not engaging correcty and thats why this one locks up first. I agree thats its possibly the shoes also but you really need to check all 4 wheels before you go replacing parts. Hows the drum look? Any stress cracks or heat discolorations? Lots of things can affect good braking. Check all the springs also.

Drum brake diagnosis is becoming a lost art.
You also have multiple issues.
Chrips are usually due to the shoes not pressing smoothly on the drum. This can be hard spots in the drum, a bent axle or backing plate, or other bent components causing the shoes to move or twist when against the drum.
Engaging first and more is something different. Check the adjustment at all 4 corners, and make sure the components are the same size and installed the same on both rear. Leading shoe is the same, wheel cylinder is the same bore, same hardware and age? After all this has been checked, there may be other issues, let us know what you find.

Wow, thanks for all of the replies. I don't think the linings have been contaminated. The wheel cylinder had some seepage, but not enough to actually get on the linings. I would believe that the wheel isn't adjusting properly. When I replaced the wheel cylinder, I felt like the self adjusting system wasn't quite right. maybe the PO messed this up, I am not sure. What is an "anti chirping spring", and what does it look like? Does anyone have a good diagram of the brake system? I have been afraid to pay for a reprinted service guide for fear that its a poor quality photocopy.

An all drum brake system is new to me and I never had any issues with any of my disc brake vehicles. The brake components look good. New springs and liners and the drums look to have been turned. No discolorations or cracks either. If I don't jam on the pedal, I can stop just fine. If I get on it, the right rear locks and I skid, even at low speeds. Either that wheel is working correctly and the others aren't, or, all of the others are fine and that one is engaging early. Frustrating...

Looks like this but not all drums have them

https://vintage-vans.forumotion.com/just-for-fun-f35/identify-this-t16533.htm

My Gremlin had a right rear brake that would lock up before the others. Turned out to be and egg-shaped drum. Replaced it and the problem went away.

That makes sense, I'll look into that as well. I was trying to avoid buying two new rear drums, but I may have to. Thanks.

Rodstrace-

I am going to pull everything off and inspect each wheel (ugh) to see whats up. I was hoping I could hold off until I converted to disks, but, I can't drive it like this. Thanks.

Switching the drums is a GREAT idea! I would have never thought of that, you guys are the best!

You sir, are a scholar and a gentleman.

Is this an original service manual or a reprint? The reason I ask is because the quality seems very nice. I have been avoiding purchasing reprints for fear that they are just photocopies of an original.

Will do. Thanks again for the diagram.

I dont know how the Ford parts work , but after just putting larger bore wheel cylinders on my dodge in the back , I was wondering if it is possible somebody had maybe bumped up your bore size on the side thats giving you grief. This wouldnt have much to do with the chirping but maybe the lock up part if the shoes aren't the culprit.

I had a similar problem and it was the other side rear that was adjusted too loose or tight - can't remember which. It took me staring at the left rear...right rear....left rear...until I finally got it right. "Men who stare at Brake Assemblies"

That manual is well worth buying. I found a similar one for a 65 for sale over here in the UK, which was a big surprise....!!! I bought it on the off chance that it might be useful, and found that it actually contains some great info and diagrams. I used those same pictures when i rebuilt the rear drums... Parts are very cheap and it is quite a simple job to do. Mine were leaking, so i replaced the cylinders and adjusters. They work very well now....

Are the manuals that Mac's sells any good (the reprints)? I have a 64 so I get to buy the 61, 62 & 63 supplement, and 64 manual.

I am going to get the drums turned at my buddies shop. Does anyone have the minimum thickness for the rear drums on a 1964 Falcon bus?

I just swapped the drums from side to side and the problem went away. We will see what happens after driving with them like that for a while. Thanks for all the advice, I will let you know what happens.

They did not cast in the oversize until later, IIRC.
For many years, the max. oversize was .060". Newer stuff (late 80s to current) can be even less. Nowadays, they tend to make stuff lighter, smaller and right on the edge to save MPG and cost. Of course, YOU have to spend more to buy replacements!
It may have been .090" on earlier stuff. Another reason to get a manual!