Thanks for your input but neither of your descriptions matches the symptoms. If you lift the carriage and release the hoist lever, the carriage will stop raising and not drift down. When you lower the carriage and release the control lever, the carriage will drift an additional 6 to 8 inches. It's always the main hoist cylinder that drifts, no matter which stage is engaged (no channels raised, or 2 or 3 channels raised). There are no staging issues. There's no oil leakage, the piston is completely dry. The free lift cylinder is the type with the valve on the bottom of the piston. I've never had one of those valves go bad, so I'm trying to find the symptoms of a bad valve before I tear into it. Thanks again for your help, I appreciate it.