Transfer case (VG), function - GF28.10-P-0002VG

MODEL 164.1 with ENGINE 156, 272, 273, 629, 642 with TRANSMISSION 722.9 as of Model Year 2009/YoM 08 model refinement package

MODEL 164.8 with ENGINE 273, 629, 642 with TRANSMISSION 722.9 as of Model Year 2009/YoM 08

Sectional view of transfer case

Fig 1: Identifying Transfer Case Components (Sectional View)

Courtesy of MERCEDES-BENZ USA

Sectional view of transfer case (AMG version)

Fig 2: Identifying Transfer Case Components (Sectional View AMG Version)

Courtesy of MERCEDES-BENZ USA

Transfer case (VG), general

Permanent all-wheel drive has advantages not only offroad but also on roads which provide good grip. The permanent all-wheel drive increases the number of driven wheels, thus improving tire-to-road adhesion. As a result, slip is reduced and the driving power is distributed to all of the wheels. The distributed driving power results in higher traction and higher lateral stability at the driven wheels.

The standard version (model 164.1, 164.8) of permanent all-wheel drive is equipped with three open differentials (transfer case, rear and front axle). The torque split of 50:50 %between the front axle and rear axle is specified as a fixed value in the transfer case. The transfer case gear ratio is 1:1.

Using the offroad program switch (N72/1s25) (except code (430) Offroad package, AMG version) which is located in the upper control panel control unit (N72/1) the driver can activate the offroad function (modified shift characteristic) in the automatic transmission (NAG2). In addition a changed accelerator pedal curve is activated in the CDI control unit (N3/9) or ME-SFI [ME] control unit (N3/10) and the offroad ABS function in the ESP control unit (N47-5).

The driver can switch the Downhill Speed Regulation function on or off via the Downhill Speed Regulation switch (N72/1s24) (except code (430) Offroad package, AMG version) or (N72s30) (with code (430) Offroad package).

Sectional view of transfer case with code (430) Offroad package

Fig 3: Identifying Transfer Case Components (Sectional View)

Courtesy of MERCEDES-BENZ USA

With code (430) Offroad package

A permanent all-wheel drive with two lockable differentials (transfer case and rear axle) and an open differential (front axle) is used in the offroad package equipment. The torque split of 50:50 %between the front axle and rear axle is specified as a fixed value in the transfer case.

The "Low/High" function in the transfer case can be used to select two gear ratios. The on-road ratio "High" is 1:1, the offroad gear ratio "Low" is 2.93:1.

The transfer case control unit (N15/7) and the rear axle differential lock control unit (N15/9) control the two ratios. Via the Low Range switch (N72s31) which is located in the lower control panel control unit (N72), the driver can switch over between the "High" on-road ratio and the "Low" offroad ratio.

The differential locks in the transfer case and in the rear axle can be operated or adjusted by the driver via the differential lock selector wheel (N72s34).

The differential lock selector wheel is located in the lower control panel control unit.

The following control units are involved in controlling the transfer case and the rear axle:

Transfer case control unit
Rear axle differential lock control unit
Lower control panel control unit
ME-SFI [ME] control unit (with gasoline engine)
CDI control unit (with diesel engine)
ESP control unit
Fully integrated transmission control (VGS) control unit (Y3/8n4)

Further partial functions are described in :

Transfer case/rear axle differential lock control, function (with code (430) Offroad package)
Downhill Speed Regulation, function
Offroad transmission mode, function (except code (430) Offroad package)
Transfer case oil supply, function
"Low/High" shift, function (with code (430) Offroad package)
Interaxle differential lock, function (with code (430) Offroad package)
Interwheel differential lock, function (with code (430) Offroad package)

Transfer case (VG), power flow	With code (430) Off-road package	GF28.10-P-0002-05VG
Transfer case (VG), power flow	Except code (430) Offroad package	GF28.10-P-0002-05VGA
Transfer case (VG), location of components		GF28.10-P-0002-06VG
Transfer case (VG), block diagram		GF28.10-P-0002-08VG
Control of transfer case/rear axle differential lock, function	With code (430) Off-road package	GF28.19-P-3050VG
Downhill Speed Regulation, function		GF28.19-P-3600VG
Offroad transmission mode, function	Except code (430) Offroad package	GF28.19-P-3601VG
"Low/High" shift mechanism, function	With code (430) Off-road package	GF28.60-P-1000VG
Interaxle differential lock, function	With code (430) Off-road package	GF28.60-P-3100VG
Interwheel differential lock, function	With code (430) Off-road package	GF28.60-P-3200VG
Transfer case oil supply, function		GF28.55-P-3000VG