Classification of Automatic Transmissions
Automatic transmissions can be divided, among others, according to the way they are controlled. We can distinguish:
Based on the current driving parameter and engine running, these transmissions select optimal gear ratio completely mechanically and/or hydraulically. This does not lead to poor gear control, because mechanical-hydraulic regulators consider many features, e.g. engine speed, wheel speed, operating mode chosen by the driver, etc. In this type of transmissions, the most common symptoms of faults are: no drive, no reverse gear, slip during gear changes.
These types of transmissions are practically hydraulic transmissions. However, they have been enriched with elements of electrical and electronic control. Due to this, the number of parameters and locks increased, e.g. in the 1980s, 3-speed transmissions (of old type) were being augmented with fourth gear, gear reduction system, converter clutch and many other functions controlled electrically and electronically. They were controlled by solenoid valves, which were incorporated into the hydraulic systems of the transmission. This increased the number of parameters and locks taken into account when controlling gears.
Hydraulic boxes with electronic control
This group of automatic transmissions is currently popular in new cars. They are equipped with electronic control, where only the actuators and the most important locks remained mechanical and hydraulic. The control and control functions are performed entirely by the electronic system, i.e. a computer built into the main engine computer. This system controls the transmission hydraulics using the entire valve assembly. The difference between hydraulic-electric transmissions is that no mechanical-hydraulic regulators are responsible for maintaining key pressure parameters and hydraulic operation. Instead, the element responsible for it is the loop, which includes: sensors, a computer, pressure control valves. In this type of transmissions, the most common symptoms of a fault are: slip during gear changes, electronic failure resulting in only 3rd gear being put in, hard gear shifting, jerking at 60-70 km/h.
Variators (variable transmissions)
These transmissions are based on a variety of technical solutions, but their main difference from to the previously mentioned groups of automatic transmissions is the lack of adjustable gear ratios. There is a constant gear change here using hydraulic methods or gears with variable gears, including belt or chain and CVT wheels. They have difficulty transferring high power and moments, so this type of transmission is rarely found in cars. Instead, they are mounted in majority of scooters. Symptoms of faults in this type of transmission are: no drive, resistance on the gear lever.
Mechanical boxes with electronic control
This is a relatively new model of automatic transmission. It is a mechanical, electronically controlled six-speed transmission (MPC). It provides driving comfort and lower fuel consumption. Various gear shifting modes (shifters under the steering wheel, sequential shift lever, automated mode) were introduced here, and the clutch pedal was removed. This automated shifting and clutch shifting reduces fuel consumption by a few percent compared to a mechanical gearbox. Savings in use are also increased by the sixth gear ratio. If necessary and if the user prefers to, it is also possible to drive in manual mode. The MPC transmission is an alternative to both traditional mechanical transmissions and traditional automatic transmissions.