Causes of rear brake pulsation other than drums?

[Wellington]

A few suggestions:
First I was going to suggest turning the drums, which you claim you did.
Is the hub a reasonable fit on the stub axle, no play?
Is the center hole on the drum a snug fit on the hub?
Is the bore in the hub square to the hub face?
Are the hub face and drum contact faces perfectly flat and clean?

[zuhandenheit]

Thanks. Yes, I replaced the drums three times over the years. I had one set turned by a machinist (the last set) and i currently have new zimmerman drums (not turned).

If there's play in the hub, I do not feel it in the wheel. But I have never removed the hubs or looked at the bearing, except by checking for play in the wheel. (Only about 100k miles on the chassis of the van.)

I very thoroughly cleaned the hubs a few times to ensure a good fit. There's no rust, and never really was any. But I cleaned the face of the hub thoroughly with emery cloth and took the drums on and off and on and off attempting to verify proper contact. At one point I bought some washers that would fit over the studs against the face of the hub, and then installed the drums, so that the drum would be spaced very slightly off the hub. This made no difference in the pulsation. (Not safe, perhaps, but I just went for a careful drive around the block and then removed the washers.)

This Q - "Is the bore in the hub square to the hub face?" I am not sure I understand, or I don't know how I would check.

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Wildthings -- My best guess is that yes there's something going on with the hub - drum relationship. I've done my best to ensure it's not just a matter of uneven mating. I can't work out what the next step would be, other than replacing the hubs, if this is the case.

[?Waldo?]

Given all that you have done, I also have to assume that the faces of the hubs are not true (perpendicular to the axis of rotation) and when you bolt on the drums they are distorted out of true regardless of the accuracy of the machining on the drums. You could test that with a dial indicator prior to removal of the hubs.

[zuhandenheit]

Thanks, Waldo -- I just bought a magnetic stand for my dial indicator. I'll report back.