My 1995 F450 dump truck-dump goes up, won't go down

[4570Man]

Most dump truck have single acting hydraulic cylinders. The pump fills the cylinder, through a one way valve, raising the bad. There is typically a valve to drop the bed which allows the hydraulic fluid to bypass teh one way valve and flow out of the cylinder, and back into the reservoir.

Are you sure it is PTO operated? There are a lot of different ways to make it work, depending on what else is on the truck. I’ve sent a few of them: air over oil, on truck with air brakes; an electric lay driven hydraulic pump, a hydraulic pump belt driven with an electric clutch. PTO driven pump with an electric clutch.

Pictures would help a lot.

Some of the lighter duty trucks have duel acting cylinders. We definitely need some pictures otherwise we’re just grasping at straws. But given the OPs previous description I’m guessing we have a low tech hydraulic valve under the truck that’s cable operated and the cable is failing to operate the valve.