does anyone know if the top motor or cylinders of a lebaron convertible have valves internal to them to prevent "leakdown", or backflow, when the top is in the raised position ? this is being asked because a friend of mine fabbed a really cool dumpbed feature for my cousin charley's model A roadster pickup using this mechanism from a late 80's-early 90's lebaron convertible. it works fantastic ! has loads of power to raise and lower the bed, but seems to have an internal leak, or backflow when the bed is in the raised position. it will [very] slowly start to lower by itself, seeming to start with the driver's side cylinder. what years used these cylinders ? it is a very cool setup, and i'll be getting pics today or tomarrow