Electronic Torque Manager Differential - External View
| ITEM | DESCRIPTION |
|---|---|
| 1 | Front mounting points with insulators |
| 2 | Differential locking motor |
| 3 | Cover |
| 4 | Filler/level plug |
| 5 | Rear left halfshaft oil seal |
| 6 | Oil temperature sensor |
| 7 | Input flange |
| 8 | Differential oil cooling inlet connection |
| 9 | Breather |
| 10 | Rear right halfshaft oil seal |
| 11 | Carrier |
| 12 | Differential oil cooling outlet connection |
| 13 | Rear mounting points |
The Electric Torque Manager (ETM) differential is a conventional design using a hypoid gear layout.
The ETM differential housing is made of aluminum and split longitudinally to a cover and a carrier. The cover is sealed to the left side of the carrier with recommended sealant and secured with 12 bolts. The cover and carrier have cast fins, which assist rigidity and cooling. The breather is installed to the top of the carrier.
An input flange is installed on the externally splined outer end of the pinion shaft, retained by a nut.
The ETM differential contains a quantity of oil for splash lubrication of the internal components. A filler/level plug is installed in the cover. The drain plug is located in the differential cooler pipe.
The pinion shaft has a hypoid gear at its inner end, which mates with the crown wheel drive gear.
The crown wheel drive gear is located on the differential case and secured with 10 bolts. The differential case is mounted on taper roller bearings located in machined bores in the carrier and the cover. Shims are installed behind the bearing cups to apply the correct bearing preload and hypoid backlash.
The differential case has a through hole, which provides location for a cross shaft. The planet gears are installed on the cross shaft, with thrust washers between the planet gears and the differential case. Circlips are secure the cross shaft to the differential case.
The sun gears are located in pockets in the differential case and mesh with the planet gears. Belville washers are fitted between the sun gears and the differential case and set the correct mesh contact between the planet gears and the sun gears. Each sun gear has a machined bore with internal splines and a machined groove. The splines are transfer the torque to the rear drive halfshafts. The groove provides positive location for the snap ring installed to the inboard end of the rear drive halfshafts.
The halfshaft seals are installed in the carrier and the cover to seal the rear drive halfshafts.
The ETM differential also incorporates a locking and torque biasing function to give improved traction performance and vehicle dynamic stability. Operation of the ETM differential is controlled by the Rear Differential Control Module (RDCM).
The basic construction of the ETM differential is similar to a standard rear differential.
The ETM differential has the following additional parts:
- A multiplate clutch and actuator assembly installed on the left sun gear.
- A differential locking motor and reduction gearbox, attached to the cover.
- An oil temperature sensor installed in the cover.
The multiplate clutch is contained in a clutch basket attached to the differential carrier with the crown wheel securing bolts. Alternate plates of the clutch pack are keyed to the clutch basket and the left sun gear. A pressure disc is installed on the outer end of the clutch pack and keyed to the clutch basket. A thrust race on the end of the clutch basket incorporates lugs which extend through the clutch basket onto the pressure disc.
The actuator assembly is mounted on bearings on the outboard end of the clutch basket, against the thrust race. The actuator assembly consists of input and output actuators separated by 5 ball bearings. A locking pin in the cover engages with a slot in the output actuator to prevent it turning, but allowing it to move axially. The input actuator engages with the reduction gearbox and is free to rotate relative to the cover.
Ball bearings locate in curved grooves in the mating faces of the input and output actuators. The bottom surface of each groove incorporates a ramp. Rotation of the input actuator forces the ball bearings up the ramps in the grooves and induces an axial movement in the output actuator. The thrust race and pressure disc transfer the axial movement from the output actuator to the clutch pack.
Sectional View - Electric Torque Manager Differential
| ITEM | DESCRIPTION |
|---|---|
| 1 | Actuator |
| 2 | Multiplate clutch |
| 3 | Differential |
Differential Locking Motor
The differential locking motor is a 12 V Direct Current (DC) motor. The differential locking motor adjusts the frictional loading of the sun gear multiplate clutch via the reduction gearbox and the actuator assembly. The RDCM controls the differential locking motor via hardwired connections. Adjusting the frictional loading of the multiplate clutch adjusts the locking torque between the crown wheel drive gear and the sun gear.
The differential locking motor is secured to the reduction gearbox with 4 bolts. The reduction gearbox is located in position on the cover with 2 dowels, and secured with 4 bolts. An O-ring seals the joint between the motor and the reduction gearbox.
The motor is driven by a 12 V DC power supply directly from the RDCM.
The differential locking motor also incorporates the following connections with the RDCM:
- A motor temperature sensor, to prevent motor damage from overheating during excessive use.
- There are 2 Hall effect motor position sensors to enable closed loop control of the motor.
The oil temperature sensor provides a differential oil temperature signal to the RDCM. By monitoring the differential oil temperature, the RDCM prevent the differential oil from overheating, which can cause damage in the multiplate clutch.