Don't know if diesel is relevant to my brakes question, but here goes (1986 f250, 4x4, 6.9, 8 lugs -- I've put about 3,000 miles on this truck in the two years I've owned it -- my first 4x4 and diesel). I started working on my front brakes a few weekends ago because the front wheels were getting hot and I felt like the truck maybe wasn't coasting as freely as it should.
The project continues, having put new calipers in the front and cylinders and shoes in the rear, and doing a lot more brake bleeding than I've had the pleasure to do before. I'm a parts replacer, not a mechanic. Now all my wheels are hot, especially the left rear which gets frying pan hot. And the truck feels like it isn't rolling freely with the clutch depressed. (Is that a 4x4 or diesel thing?.) I adjusted the brake booster pusher thingy, aiming to err on the side of shortening it too much.
With the ebrake disengaged (it's not working at all) the rear on jack stands, and the self-adjuster fully retracted, I can't manually rotate the wheels. Shouldn't that be fairly easy? When I most recently reinstalled the drums I dialed up the self-adjuster so that when the drums went on it required just a little effort to send them home. (I was hoping this would help the ebrake do it's job, but nyet.)
I REALLY don't get the ebrake. The mechanics that are supposed to force the shoes apart seem very sketchy -- there's almost nothing on the rear brake shoe for the pivoting part to push against. Did I get wrong shoes?

 

The rear wheels should freely spin when they’re in the air. The amount of drag you describe sounds like too much. When I first did mine, I put them on with a “little” drag. 15 min down the road my wheels were smoking. Did you reuse the old star wheel adjuster at the bottom between the shoes? The new motorcraft ones are a smidge longer, and even screwed right in are too long causing too much drag. That was my issue, I assumed they were the same length and threw em in. Not so.

I put my drums on with the absolute slightest drag, and I mean slightest. Put them on a bit on the loose side, and tighten through the peep hole when desired pedal travel is reached and they’re warm instead of hot. It’s easier to tighten through the hole than loosen, as you have to disengage the self adjusting lever with a flat blade, then try and turn the adjuster back to loosen. No room for more than one tool at a time back there.

Drums on the loose side will cause a delay in braking and a longer pedal travel, test them in the yard first lol. Before adjusting anything else, try and get the rear brakes working properly. They will usually solve most of the braking problems on these trucks.

Is the wheel cylinder pushing the shoes apart at the top? With the star adjuster at the bottom tightened in, the shoes shouldn’t be touching the drums. Those cylinders like to fail when they get old too.

 

Here is a YT Vid that might help you.
There is a tool to measure the inside of the drum and then the shoes.



Charlie