I have the hydraulic cylinder rebuilt for my dump truck and I did the install and removal, the shop told me just reconnect the hoses and run the bed up and down about 10 times and you should get rid of all the air in the lines. Well I think all the "air" is out for it goes up and down no problem except when going up it shakes, kinda bad to. I when back the shop that rebuilt the cylinder and he told me there's still air in the lines and to keep running the bed up and down. Well its been up and down about 100 f@#ing times and its still doing the same thing, what else should I do. The bed is power up power down.