The main nodes of the AT are: torque converter (torque converter), planetary gear, hydraulic or electronic control units. To switch to another gear ratio in the planetary gearbox, hydraulic disc and band brakes and disc clutches are used.
The torque converter has the same function as a hydraulic clutch. Its task is to carry out the clutch at the start of movement and gear changes. The hydrotransformer is equipped with the blocking coupling which is carrying out direct coupling of the engine with АТ.
The automatic transmission control system is interfaced with the engine management system via the CAN bus and based on the analysis of data from various information sensors (not necessarily directly related to the functioning of the AT itself), selects the optimal mode of operation of the AT from the point of view of efficiency, smoothness of switching and other things. AT has its own control unit (TCM). If a malfunction is detected, the corresponding code is written to the memory of the control unit (see Specifications to the head Engine Electrical Systems).
The only AT maintenance procedures that should be performed on a regular basis is checking the level of its working fluid (ATF) and ATF replacement. The procedure for performing these procedures is described in Sections Checking fluid levels, leak control and AT transmission oil change (respectively) Chapters Vehicle settings and routine maintenance.
Thanks to the use of D / V modes «P» / «N» (PNP sensor) the engine can only be started when the AT selector lever is in position «R» or «N», which prevents accidental movement of the car when trying to start.
When the sensors used by the TCM unit fail, the AT switches to emergency operation. In this case, the car can engine forward only in 4th gear. E/m valves of a gear change are de-energized.
This Chapter provides only general information on the operation and design of the AT.
AT repair associated with its disassembly should be entrusted to specialists.