I'm having a bit of trouble with the brakes on my 89 F-350 dooley working a little too good. It's like an all or nothing thing. As soon as they start to grab at all, they grab real hard. Not quite enough to slide the tires, but definately more than is normal. This feels like it's happening on the back axle only. Any ideas of what might cause this?

if they are not locking up i wouldnt be too alarmed but if it seems more than normal than check to see that your axle seals arent leaking , that will make the rear brakes grab more than normal and does happen on these axles from time to time.

remove your drums and clean your shoes and lube them - a lot of problems like your happen from poor lube of the shoe to the backing plates - hight temp grease ( a little !! ) or some anti seize - then adjust them - - my 95 f250 does that when it sits for a week or so