Torque is transmitted from the crankshaft through the clutch to the primary shaft of the gearbox, the end of which is provided with splines on which the friction disk of the clutch is put on. From the output shaft of the gearbox, power is transmitted through the cardan shaft to the main gear of the rear axle.
The primary and output shafts of the gearbox are installed coaxially. The gears of the primary and output shafts are in constant engagement with the gear block of the intermediate shaft. The gear selection is performed by moving the synchronizer hubs, which connect the corresponding gears of the output shaft to the output shaft.
Gear shifting is accomplished using a floor-mounted lever and gear selection mechanism (in some models, gear shifting is accomplished using a switch mounted on the steering wheel). Some models can be equipped with a "sport shift" system. On these models, gear shifting is also carried out using a lever or a button on the steering wheel. In addition, on these models, gear shifting can be carried out automatically using an electronic control unit. The control unit controls gear shifting and clutch (via hydraulic actuators) depending on road conditions and driving style.
Some models have a "acceleration control" system. When you press a button, an electronic unit is activated that controls the engine speed, clutch and gear shifting, achieving maximum acceleration of the car. You can get more information about this system from your dealer or in the owner's manual for your car.
When the shift lever is pressed, the corresponding gear selector mechanism shifts the synchronizer hub along the shaft until it engages with the gear pinion of the gear being engaged. Since the synchronizer hubs are mounted on the splines of the output shaft, this connects the gear to the shaft, which ensures the transmission of torque. To ensure fast and smooth gear shifting, synchronizers are available on all forward gears. The synchronizers include locking rings, spring-loaded pins, as well as synchronizer pinions and hubs. Synchronizing cones are made on the ends of the gear and locking rings.
When a car is manufactured, oil is poured into the gearbox that does not require replacement during the entire service life of the car. At least, the manufacturer does not give any recommendations on the frequency of oil replacement.
[The original text of the article is available on the resource: «BMWMAN.ru»]