A gearbox is an assembly which is designed to convert and transfer torque from the engine to the drive or propeller shafts, thus ensuring the rotation of the wheels.

It is also used to engage the reverse gear.

Design of a gearbox

A manual gearbox consists of shafts and gears with different numbers of teeth. In modern assemblies, gears of adjacent shafts are constantly in contact. Engaging the required gear is carried out with the help of special synchronisers. The required synchroniser is activated by the corresponding shift fork which is connected via arms and joints to the gear lever located in the cabin.

An automatic gearbox comprises gears of various sizes which form an epicyclic gear train. Clutch packs are responsible for the engagement of the required gears. Their connection is ensured by pumping the working fluid into the corresponding channels of the hydraulic unit. Torque from the engine is transferred to the gearbox with the help of a hydraulic torque converter.

A continuously variable transmission is stepless. Its main working elements are cone pulleys located in pairs on the input and output shafts with a tensioned steel belt around them. Pulleys can come together or separate, changing their working diameter this way and, consequently, the transmission ratio. Their design also has an epicyclic gear train responsible for driving in reverse. The movement of the pulleys is ensured by a hydraulic torque converter, an electronically controlled multi plate clutch, or other mechanisms.

Maintenance advice

• Do not ignore oil change intervals. Check the oil level regularly. Contaminated lubricant along with an insufficient amount thereof cause premature wear and tear of moving parts and the gradual deterioration of the gearbox.
• It is important to ensure proper clutch operation in vehicles with a manual transmission. If dampers are faulty, loads on the gearbox increase significantly.
• Avoid rough acceleration and braking. They have a devastating effect on the components of the transmission .
• It is not recommended to use a car with an automatic transmission for towing other vehicles. The gearbox may overheat and fail.
• During wintertime, you should warm up your gearbox thoroughly before setting off if you have an automatic transmission.

Malfunction symptoms

If issues occur when shifting gears in manual transmission, they might indicate worn-out synchronisers or gears, an insufficient amount of oil in the assembly, or a faulty selector rod, cable, or lever. Worn-out sleeves and splines or a failing rod or fork can be accompanied by spontaneous disengagement of the clutch. A worn input shaft bearing usually produces noises when in neutral. In vehicles with an automatic transmission, the friction plates and splines of the turbine wheel can wear out, the blades of the torque converter wheel may break and valves can become clogged. These malfunctions cause slipping. Jerking during acceleration in vehicles with a CVT might be a consequence of failing oil pump valves. Humming or growling noises indicate worn-out bearings.

Malfunction causes

The wear and tear of bearings, splines and gears, clogged passages of the hydraulic unit, stuck valves, and worn-out belts are the most frequent consequences of not changing your oil on time. Accumulated dirt clogs the channels of the hydraulic unit and forms carbon deposits on the components that then act as an abrasive. Improper use of your vehicle might lead to the deterioration of ball joints and bearings and also cause the gearbox to overheat.

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