2007 gearboxes

2007 CV of the CVT

While the first 50 years of tractors focused on developing engines, the following 50 years has focussed on developing transmissions. The result of all this development work is the stepless or “continuously variable transmission”, CVT for short. CVT transmissions solve many issues related to usability, efficiency and optimum ratios.

The CVT acronym can also be extended to PSCVT for “power split continuously variable transmission”, as all stepless transmissions on agricultural tractors today comprise both the mechanical and hydrostatic transmission components.

Valmet tractors traditionally used mechanical transmissions, like other tractor brands, but it also introduced hydrostatic transmission components. The Valmet 565, was launched in 1966, and was available with an optional creeper gear. When the creeper gear was engaged, a hydraulic motor helped spin the gear, allowing the speed to be adjusted steplessly between 0 and 3 km/h.

The next stepless transmission came with the Valmet H800, which featured a fully hydrostatic transmission. Each wheel on the tractor had a three-speed radial piston hub motor and variable displacement pump. The differential lock was operated by valves, allowing the same amount of oil to flow to each wheel. The rear PTO shaft was also powered by a hydraulic motor, so the tractor had no fixed mechanical transmission at all. The driver could adjust the speed using a lever or the pedal, which was referred to as the “speed pedal” instead of a “gas pedal” for the first time in connection with the H800 model.

Valtra’s experience with hydrostatic transmissions therefore stretches back half a century already. The Direct transmission, that was launched in 2008 combined the hydrostatic and mechanical gearboxes on the same PTO shaft. This enabled the exact properties required for the optimal performance of tractor tasks.

T202 Direct snow ploughing

Valtra 202 featured the modern CVT transmission called Direct, which is a combination of mechanical and hydrostatic drive.

Valmet H800

The Valmet H800 featured a fully hydrostatic transmission with no fixed mechanical transmission at all.

Valmet 565

The hydrostatic creeper gear was introduced with the Valmet 565 in 1966.