brake issue

[54bobby]

guys, maybe one of you can point me in the right direction. my son's been driving the manchee (87, 2.5 long bed, front disc rear drums). he said the brake peddle feels soft so i took it for a drive and it is. in a gravel lot, i hitem pretty good and only the fronts locked up in the gravel. seems to me the rears arent working. they're only 2 years old and the truck dosen't get used that much. peddle is real soft and truck dosen't wanna stop. could it just be adjustment? MC is full although the larger compartment looks dirty. not loosing any fluid. could it be a clogged brake line? i'm working 70 hours a week and that's why i'm asking for a starting point. just don't have any time.

[HOrnbrod]

Starting point is to jack up the rear wheels off the ground, put the transmission in neutral, and adjust the brake shoes on both sides with a brake spoon so they just slightly drag when rotating the wheel by hand. It could be caused by other things to, but this is the first thing I'd do if I had rear drum brakes.

[1989 Eliminator]

I would do what hornbrod said but also clean all the drum brake components very good. Also put anti-seize on the adjuster screw so that can move easily. Those often get rusted together and will not turn; making your rear brakes not adjust.

[Eagle]

Don't overlook the rear height-sensing proportioning valve. If it has been disconnected or improperly adjusted, it may be reducing the amount of braking to the rear to almost nothing.

[54bobby]

Don't overlook the rear height-sensing proportioning valve. If it has been disconnected or improperly adjusted, it may be reducing the amount of braking to the rear to almost nothing.

i've heard of these valves but in the 5 years i've had the truck, it's never been screwed with. would/can they just go bad and lead to my condition?

[fiatslug87]

Make sure yours does not look like this. This can happen when the body is lifted by the frame and the axle sags, as the vehicle is lowered the valve can orient incorrectly.

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Should look like this (Hornbrod's picture)

[gogmorgo]

As long as the valve is hooked up, it's opening and closing partially as the rear suspension cycles, so it can always wear out. As far as adjusting the rod, I think the only way that could happen is if the rod gets bent, which if anything would just increase rear braking. Also the above.