Transfer Case Oil Cooling System, Function - GF28.55-P-1002AVM

Model 217, 222 with transmission 725.096 

View of transmission oil cooling circuit 

Courtesy of MERCEDES-BENZ USA

Function requirements for oil cooling system in general 

• Circuit 87 ON
• Internal combustion engine running
• Vehicle driving

Oil cooling system in general 

In order to keep the operating temperature of the transfer case constantly low, the oil pump (10) integrated into the transfer case is used.

The transmission oil temperature can be lowered by the oil cooling system and can help prevent damage to the transfer case due to overheating.

Transmission oil heat exchanger

The transmission oil heat exchanger is designed as a plate-type oil cooler. Its operating principle means it can be kept small and provide high efficiency when cooling the transmission oil.

Function sequence for oil cooling system 

The transmission oil is pumped by the oil pump in the transfer case to the transmission oil heat exchanger. The transmission oil heat exchanger forms the interface between the transfer case oil circuit and the coolant circuit. The waste heat of the transmission oil is absorbed by the coolant within the transmission oil heat exchanger (plate-type oil cooler). The transmission oil flows from the transmission oil heat exchanger back to the transfer case.

Control of coolant inflow

The circulation pump 3 for the low-temperature circuit (M43/8) is actuated as required to match the oil temperature of the automatic transmission and the oil temperature of the transfer case. It pumps the coolant for cooling to the automatic transmission and the transfer case. The oil temperature of the transfer case is transmitted via a direct line from the transmission oil temperature sensor (B91) to the all-wheel drive control unit (N45).