A vehicle PTO driveline (10) in which a PTO input shaft (11) drives a PTO wet clutch (12) which when engaged drives a PTO output shaft (13). The driveline has an eccentric formation (34) on the input shaft (11) which oscillates a pumping piston (31) when the input shaft rotates, which piston pumps cooling/lubricating fluid from a reservoir (25c) to the wet clutch (12). The piston is connected with the eccentric formation by a ring (33) which surrounds the eccentric formation (34) and a hollow tube (32) which is attached to the ring and which carries the piston at a lower end, the piston oscillating inside a chamber (31a) when the input shaft rotates. The chamber (31a) is connected with the fluid reservoir (25c) and the oscillating piston pumps the fluid along the hollow tube (32) into the ring (33) which then delivers the fluid into internal passages (38) in the input shaft from where the fluid flows to the wet clutch.