Ok guys need ya' to school me on how to adjust the rear bracks on my 53 6400.

Here's the background.
Over thanksgiving I figured I'd try to get the brakes working on this truck so far I've not been too worried about them just driving it around the farm and in the fields at the farm, as the handbrake stops it fine, and the regular brakes work consistently after 4 pumps. The truck hasn't lost any fluid since we got it. We went ahead and bled the system at each wheel as we figured it was just some air in the lines. It had a little but all of them bled out fairly quickly and none of the bleeder screws were stuck.
Near as we could figure maybe the brakes hadn't been adjusted in a very long time and it was just taking 4 pumps to get them out to where they caught so I adjusted the fronts via the normal screwdriver in the slot method (they adjusted a long way out but then caught good). But I couldn't figure out how to adjust the duals in the back. I'm new to the big trucks so this is prob. simple and I just haven't run across it yet.

I did pull the drum on the front left and the pads look like they have alot of life left so I'm hoping this will be the quick fix.

Also the truck has a hydrovac and I've got no idea how it works or if it's working.

Thanks,
MONGO


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