Oil Supply For 4Matic Transfer Case Function - GF28.55-P-3010AVN
Model 257 (except 257.361) with transmission 725.0
up to model year 2021
View of oil reservoirs
View of oil hole at vehicle standstill
Function requirements for 4MATIC transfer case oil supply, general
- Vehicle is moving or rolling
Oil supply for 4MATIC transfer case, general
The oil supply system ensures that the components of the transfer case are sufficiently greased and cooled.
The flange-mounted construction means that the transfer case and automatic transmission have a separate oil system. The following oil reservoirs are present in the transfer case:
- Tank compartment (1)
- Differential gear system compartment (2)
- Front axle transmission output compartment (3)
The tank compartment (1) and the front axle transmission output compartment (3) are connected through oil holes (4). When the vehicle is stationary, the oil level is identical in both of these compartments.
Function sequence for 4MATIC transfer case oil supply
The oil supply is designed as a splash oil supply.
View of oil supply in differential gear system compartment
View of oil supply in differential gear system compartment
In driving mode the oil is pumped out of the differential gear system compartment (2) through the rotation of the planetary gear differential (5), spun upwards into the drip trough (6) of the transfer case, and routed through the oil duct in the front axle transmission output compartment (7) up to the transverse passage (8). The accumulated, excess oil runs directly back into the tank compartment (1).
View of oil supply for thrust bearing/radial bearing on front axle transmission output
View of oil supply for radial bearing on front axle transmission output
View of oil supply for planetary gear differential
The volumetric flow rate is distributed from the transverse passage (8) to the thrust bearing for the front axle transmission output (9) and to the planetary gear differential (5) thereby lubricating these components.
The oil from the tank compartment (1) is pumped through the tank compartment oil hole (10) and the existing tank compartment oil duct on the front axle transmission output (11) to the thrust bearing on the front axle transmission output (9) and to the radial bearing on the front axle transmission output (12). This then assures that both bearings are lubricated. The oil is forwarded by the pump action from the thrust bearing on the front axle transmission output (9) into the front axle transmission output compartment (3).
View of oil supply for the load change damper and planetary gear differential, gears on the drive gear for the front axle transmission output and output gear for the front axle transmission output
View of oil supply from load change damper and planetary gear differential
View of plastic nozzle
The tooth engagement of the gears on the drive gear for the front axle transmission output (14) and the output gear for the front axle transmission output (15) causes the oil to be routed from the drip trough for the front axle transmission output compartment (13) via the plastic nozzle (16) straight to the disks of the load change damper (17), the bearings and the gear meshing of the planetary gear differential (5). Once there, it is routed by the centrifugal force to the outer wall of the differential gear system (2). The oil then gathers in the drip trough (6).
View of ventilation system
Ventilation occurs through the ventilation system inlet, the inlet bore (20), the vent tube (21) and the ventilation system outlet (22). The oil runs through the drain slot (19) into the front axle transmission output compartment (3). The pressed-in vent pipe (21) prevents any oil from escaping at the ventilation system outlet (22).
Oil change and oil level check, connecting screw screwed-in
Oil change and oil level check, connecting screw unscrewed
For an oil change or an oil level check, the tank compartment (1) must be connected to the differential gear system compartment (2). This is made possible by unscrewing (approx. 8 mm, up to end stop on the drain screw (24)) of the connecting screw (23). The connecting screw (23) must not be fully unscrewed. This would lead to a loss of oil. After the oil change or the oil level check, the connecting screw (23) must always be screwed completely back in again. A connecting screw (23) that is only partly screwed in will lead to total failure of the transfer case.
| Overview of system components of permanent all-wheel drive | GF28.00-P-9997AVN |