A pull-type crop harvesting machine has disk cutter carried on a framemounted on ground wheels with a hitch arm extending from the frame over theheader to a hitch connector of a tractor. The hitch arm is mounted for pivotalmovement about a generally upright axis such that in a first position thetractor towsthe frame in echelon to one side and in a second position the tractor tows theframein echelon. The disks are hydraulically driven by a pump at the front end ofthe hitcharm and a motor at the frame with the hydraulic circuit including a sump tankdefinedby a hollow interior of the hitch arm and a cooling radiator defined by atubular framemember which is preferably located at the disk drive as a support therefore asit iscooled by the air flow from the disks and contact with the crop and carries alowvolume of fluid.
