- Distribution box.
- cardan shaft.
- Differential clutches.
- Limited slip differential.
- Rear differential clutch control unit.
The transfer case is located to the right of the gearbox to which it is bolted. Its purpose is to transfer power from the gearbox through the driveshaft to the rear differential clutch.
The cardan shaft is used to transmit torque from the transfer case to the differential clutch. It contains three pipe sections, a front Rcepp joint, two cardan joints of unequal angular velocities in the central part, and a rear Rcepp joint. The support bearings of the cardan shaft are installed behind the cardan joints in rubber bushings placed in brackets, which, in turn, are bolted to the bottom of the vehicle. The position of the brackets during the production of the car is selected with great accuracy. The cardan shaft does not run in a straight line between the transfer case and the differential clutch, but has smooth kinks to avoid vibration. If the support bearings are not installed accurately, vibrations may occur when the vehicle is moving.
The cardan shaft is connected to the transfer case gear shaft by means of splines on the Rcepp front joint shaft. This hinge is designed to smooth the angle of fracture between the transfer case gear and the cardan shaft, as well as to compensate for the mutual movements of the units in the longitudinal direction.
The cardan shaft is connected to the differential clutch driver by means of a rear constant velocity joint, which is designed to smooth the fracture angle between the differential clutch driver and the cardan shaft, as well as to compensate for the mutual movements of the units in the longitudinal direction. The Rcepp rear hinge is welded to the rear span of the cardan shaft and forms a single unit with it.
Rcepp's hinges have an outer race, which is also called the hinge body. Inside the clip there are six hemispherical grooves. The inner cage of the hinge consists of a cylindrical section, along the edges of which there are also six hemispherical grooves. The inner cage is inserted inside the outer one, and between them six balls are placed in the grooves, due to which the torque is transmitted from the inner to the outer part of the hinge of equal angular velocities. The ball separator is installed between the outer and inner races.
Central universal joints of unequal angular velocities (Polhem hinges) are installed between the central and middle, as well as between the middle and rear spans of the cardan shaft. They are designed to transmit torque at an angle between units that have relative movement. To prevent vibrations, the cardan joints are placed at an angle of 45°relative to each other.
The Polhem universal joint consists of two forks made of hardened steel and connected by a cross. The cross pins are mounted in bushings pressed into the forks by means of needle bearings. The bushings have a special synthetic molybdenum disulphide lubricant incorporated at the factory. The forks of the cardan shafts are welded to the corresponding pipe spans and form a single unit with them.
The differential clutch is designed to control the transmission of torque to the rear wheels. Torque supply to the rear axle of the car varies from 0 to 100% through a hydraulically controlled multi-plate clutch. The differential clutch is attached to the limited slip differential with four bolts.
The limited slip differential, also called the rear drive unit, is located in the subframe and has drive shafts leading to each of the rear wheels. The limited slip differential is fully mechanical. It consists of a hypoid gear and the differential itself. The limited slip differential clutch, if equipped, is attached with six bolts to the left side of the limited slip differential. It is designed to completely or partially block the left drive shaft relative to the differential housing for even distribution of torque between the rear wheels of the vehicle. Limited slip differential clutch of disc type with electro-hydraulic control.
The hydraulic pump consists of a motor and a pump housing. It is controlled by the rear differential clutch electronic control unit. The motor drives a five-cylinder axial piston pump, which creates a working pressure of 2700-3200 kPa. The pressure control valve is also electronically controlled and serves to regulate the pressure supply (from 0 to 3000 kPa) to the working piston. It is directly connected to the rear differential clutch control unit, which provides a pulse width modulation signal. The rear differential control unit activates the hydraulic pump when the ignition is switched on and the engine is started. The pump is operated until the required operating pressure of approximately 3200 kPa is reached. The pressure value is determined by measuring the energy consumption of the pump motor. The higher the pressure, the more resistance the pump drive motor experiences, and the more current it consumes. After the system pressure reaches approximately 3,200 kPa (fully charged battery) the accumulator piston opens the bypass and the pressure is no longer built up, as a result of which the current consumed by the electric motor does not increase, but remains at a constant value. After that, the control unit comes to the conclusion that the maximum pressure has been reached and turns off the pump. If the pressure drops to 2,700 kPa, the pump is switched on again.
The rear differential clutch control unit is mounted on the crankcase of the rear drive unit. Based on information from the data bus, the rear differential clutch control unit calculates the distribution of torque between the front and rear axles of the vehicle, as well as between the rear wheels in versions with a limited slip differential clutch. The rear differential clutch control unit and check valve are calibrated together and should only be replaced as a set.
The rear differential clutch control module monitors communication bus data, input and output signals, detects mechanical failures and internal failures of the control module. When malfunctions are detected, a diagnostic trouble code is generated.
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