Transmission and power transmission

The motor creates the power, but it is the transmission that carries it out to where it is needed: to wheels or belts that drive the machine forward, and to the tools via the power take-off. As a mechanic you must understand the different transmission principles, because they are troubleshot and serviced very differently.

A motor delivers force most effectively within a certain RPM range. The transmission adjusts the motor's RPM and torque to what the task requires — lots of pull at low speed in heavy work or higher speed in transport. It also makes it possible to engage and disengage the power and to change direction.

• 01Mechanical gearbox: fixed gears, often with a clutch that disengages power when shifting.
• 02Powershift: gear changes under load without interrupting power.
• 03Hydrostatic transmission: a pump and a hydraulic motor provide stepless speed and easy direction change.
• 04Stepless/variable transmission: combines mechanical and hydraulic power for broad work range

On tractors and many machines, power is led to implements through a power outlet — often called PTO. A rotating shaft drives, for example, a mower, a pump, or a cart. The power outlet can have different standard speeds and it is crucial that implement and machine fit together so the implement runs at the speed it is designed for.

• 01Check oil condition and oil level in gearbox and hydrostat according to specification.
• 02Listen for unusual sounds and feel for vibrations under load.
• 03Be aware of overheating — it can indicate slip or low oil level.
• 04Investigate whether the problem is in the transmission itself or in steering and operation.

When you know the difference between a mechanical powershift and a hydrostatic transmission you can choose the right troubleshooting method and avoid looking in the wrong place.