The rear differential assembly consists of a torque tube assembly, three-piece differential housing, ring and pinion, and a differential carrier assembly. (Схема №2) The aluminum torque tube housing contains an internal drive shaft that is supported by roller bearings at each end. The internal drive shaft is retained to the front propeller shaft assembly by bolts and splined to the differential pinion shaft. External to the tube are a vehicle mounting bracket and a noise and vibration dampener.
The pinion shaft is positioned in an aluminum pinion housing and is supported by tapered roller bearings. (Схема №2) A shim between the pinion and differential housings provides the proper backlash for the ring and pinion. The ring gear is retained externally to the differential carrier assembly by bolts. Both the transfer case hypoid gears and the rear differential assembly use unique type synthetic gear oil. The differential carrier assembly consists of left and right side clutch pack drum, separate left and right axle sub shafts, left and right gerotor pump components, left and right clutch packs, left and right pistons, and internal valves. (Схема №2)
The Versatrak(R) on-demand system operates as follows: The drive shaft assembly, mated to the output flange of the transfer case, is constantly rotating and spins at a rate equal to an average of the two front wheels. Under normal straight-ahead non-slip driving conditions, the external and internal gears of the differential gerotor pumps are rotating at an equal rate of speed. Under those conditions, there is no speed differential between the pump gears, no pump pressure created, no clutch pack activation, and no torque transfer. During a front-wheel slip condition, the external gears of the gerotor pumps rotate at a faster rate of speed than the rear-wheel driven internal gears. (Схема №2) The gerotor pumps pull oil from the sump through the clutch pump check valve sending pressurized oil to each individual piston to activate the separate clutch packs. On-demand torque/drive is provided to each of the rear wheels as required. A valve internal to each piston housing controls maximum clutch pack pressure. A second valve within each housing is temperature compensating and controls fluid flow based on ambient temperature. The system operates in both forward and rearward vehicle directions.
In the event a spare wheel of a smaller diameter is used on any of the four positions, the wheel rotational speed difference is detected by the wheel speed sensors of the Anti-Lock Brake System (ABS) system. The Powertrain Control Module (PCM) directs the clutch pump check valve to close and block oil flow to the gerotor pumps. The clutch pump check valve also monitors the sump oil for an over-temperature condition. If differential oil temperature exceeds 230°F (110°C), the valve will close and block oil flow to the gerotor pumps. In both spare wheel usage and over-temperature conditions, a "closed" valve will alert the PCM to illuminate the control panel AWD DISABLE light.
The All Wheel Drive (AWD) system provides On-Demand all wheel drive, distributing variable torque/power to the rear wheels via individual axle shaft assemblies. On-Demand drive is provided to each of the rear wheels only when slippage is detected at the front wheels. As long as there is no slippage at the front wheels, there is no front-to-rear speed differential and no need for rear wheel drive torque. In the event there is front-to-rear wheel speed differential/slippage, a rotational speed difference between the gerotor pump components (rotor and housing) occurs. In those instances, the rotor draws fluid from the sump and through the internal passages of the differential carrier, sending pressurized fluid to a piston (actuating the specific rear wheel clutch pack). In the event of a spare wheel (of smaller diameter) is used on any of the 4 positions, the wheel rotational speed difference is detected by the wheel speed sensors of the ABS system. The powertrain module directs the differential inlet valve to close and block oil flow to the gerotor pumps. The inlet valve also monitors the sump oil for an "overtemperature" condition. If differential oil temperature exceeds 230°F (110°C), the valve will close and block oil flow to the gerotor pumps. In both spare wheel usage and overtemperature conditions, an activated inlet valve will illuminate the control panel AWD DISABLE indicator.