Abstract: A hydraulic drive system for a three-wheeled vehicle with drive assemblies including drive units having a single drive unit with two separate directly coupled drives and a pair of transverse drive units employing respectively separate directly coupled drives. There are hydraulic feed lines for parallel operation and for series operation, a secondary hydraulic feedline between the drive units and a secondary hydraulic feed line between the drive units and a hydraulic controller controls diverter valves for parallel and series operation. The hydraulic drive includes a steering system which senses out of line travel.

Abstract: A drive controller for a hydraulic drive system, a three wheeled vehicle having a pair of transversely arranged in line of drive shaft assemblies and a single wheel drive shaft assembly each assembly including a drive unit having two separate drives and has for series operation secondary hydraulic feed lines between one of the drives of the single drive units and one of the drives of each transverse drive unit. A pressure release valve is provided in each secondary line which valve is fed through a non-return valve.