The automatic transmission includes many details that work continuously under load and hydraulic oil pressure. After a long period of use, some parts may wear out or be damaged, leading to difficulty shifting gears, incorrect gear changes or loss of some gear levels.
According to Mr. Tran Minh Tien - lecturer of Automotive Technology, Dung Quat College of Technology (Quang Ngai), one of the groups of parts that are easily eroded are the friction leaves inside the clutches of the gearbox. The friction leaves are arranged interspersed with steel leaves and have the task of creating friction to lock a component in the planetary gear set.
In principle, to create gears, the planetary gearbox needs to fix one component, and at the same time drive another component to create movement in the remaining component. When the friction leaf is worn, the ability to press and hold decreases, causing the clutch to slip. At that time, gearboxes may experience indecisive gearshift, gear slip or loss of some gears.
When checking, technicians need to determine the level of wear to replace friction sheets, steel sheets or even the clutch cluster if necessary. Not every case only replaces one detail; the repair plan depends on the actual condition of each cluster.
In addition to the clutch, the brake cluster of the automatic transmission also uses friction details to fix a component in the planetary gearbox. These details can also wear out after a long working time, affecting power transmission and gearshift capabilities.
Another group of causes lies in the hydraulic valve cluster. This cluster consists of many valves and oil lines responsible for distributing oil pressure to the clutches, brakes and corresponding actuators. Electromagnetic valves control the opening and closing of the oil line according to signals from the gearbox control system.
If the electromagnetic valve is damaged, the inner coil is broken, or the valve is jammed, the oil flow may not be controlled correctly. This condition can cause the gearbox to shift abnormally, slow to shift or not be able to enter some gears.
In addition, the oil line in the valve cluster also needs to be checked. Dirt or dirt in oil can limit the flow, causing the valve to operate inaccurately. Therefore, when repairing a gearbox, technicians often have to check both the oil condition and the hydraulic system.
Another important detail is the gearbox oil pump. The pump creates oil pressure to lubricate and supply hydraulic oil to the internal mechanisms. When the engine is not working, depending on the gearbox design, the main oil pump may not create enough pressure to lubricate and operate the system.
Therefore, when automatic transmission vehicles encounter problems and have to move, users should prioritize using floor-based rescue vehicles or the plan prescribed by the manufacturer. Do not arbitrarily pull the vehicle with active wheels contacting the road surface, as it may cause further damage to the gearbox.
In addition, using the correct type of automatic transmission oil and maintaining it according to the manufacturer's recommendations is very important. The time to check or replace the oil depends on the design of the transmission, the type of oil and the actual operating conditions.
