Hello Gentlemen, let me add my $.02.
I remember reading a few years ago in one of the truck magazines, where a project truck had a similar problem. They put a dual master cylinder on a 1956 TF truck. Granted, is is not a 1952-53 AD truck, but the concept may be similar. Anyway, they installed the dual MC, and had problems with one of the rear wheels locking up all the time. Turns out, the way the factory metal brake lines were run, and they verified this in the applicable factory service manual, was that one of the rear wheels was on a line all its own.
Meaning, when they plumbed in the new MC, both front wheels and one rear wheel were run off one chamber off the master cylinder, and the other rear wheel was run entirely off the other chamber. I don’t remember the specifics of how it was plumbed or anything like that. However, I recommend you hand over hand check the connections of all the metal brake lines and see how it is plumbed. If you do have this problem of one of the rear brakes is plumbed all by itself, you can install a Tee in the line to isolate the front from the back. This is not specific, you will need to figure the correct plumbing out. However, I think you can get the gist of what I am saying.
If you have access to a brake pressure gauge, check the pressure at each wheel cylinder with the brakes applied, and see how they compare.
Good luck!
Seth K. Pyle
