How do I determine why ram is slow or will not lift dump bed

where can i get parts for a pneumatic activated hydraulic clutch ( mark 7 capsule clutch inc. st paul Minn ) it connects a hydraulic drive motor by Commerical mounted on front of my 1989 LST 9000 Ford dump truck. The clutch is PTO driven.

PROBLEM! When i move lever in cab to lift dump bed the ram is slow to respond or sometimes does not respond. the ram is a two way up and down. when i flip switch to activate hydraulics rear of clutch goes in ( pneumatic activated ) . i have noticed that hydraulic fluid comes out of the breather on top of clutch when it dumps? I assume there must be a seal on clutch and hydraulic drive motor both that have failed to allow that to occur? i wonder if air could enter system because the two seals failed and cause the slow response of the ram. the rubber dust seal that goes around clutch also needs replacing? the clutch is about 10-12 inches in diameter. the hydraulic pump and clutch do not over heat but do warm up. there is enough hydraulic fluid in tank. i have googled name of pneumatic clutch but could not find anything. when ram extends 3 sections approximately 12 feet it moves like air is in system. there are no other leaks in system.