On a lot of the dump cylinders, the housing surrounding the ram is also the fluid reservoir. There should be a pipe plug on top of the cylinder housing that's used for filling and checking the fluid level. I've seen all sorts of fluids put into dump cylinders, but non-detergent 30 weight motor oil was once a popular dump cylinder fluid, easily accessible just about everywhere, and about the right thickness. Prop the bed up with a STURDY support, like a piece of heavy pipe, or a 4X4 wood beam, etc. Then add a couple of quarts of oil, leave the plug out, and lower the bed. Any overfill will run out the plug hole. If you put the plug back into an overfilled lift cylinder, the bed will not retract fully. Be careful!
Jerry
