eSelf Study Program 950163

Front final drive 0D4

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Audi of America, LLC
Service Training
Created in the U.S.A.
Created 1/2016
Course Number 950163
©2016 Audi of America, LLC
All rights reserved. Information contained in this manual is based on
the latest information available at the time of printing and is subject to
the copyright and other intellectual property rights of Audi of America,
LLC., its affiliated companies and its licensors. All rights are reserved to
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All requests for permission to copy and redistribute information should
be referred to Audi of America, LLC.
Always check Technical Bulletins and the latest electronic service repair
literature for information that may supersede any information included
in this booklet.

Revision 1:1/2016
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Introduction .......................................................................................2
Front final drive 0D4 .................................................................................................................................................. 2

System description..............................................................................3
Distribution of drive power ....................................................................................................................................... 5
Front axle lead ........................................................................................................................................................... 5

Component overview ..........................................................................7
Cutaway view of transmission.............................................................9
Longitudinal section A-A ........................................................................................................................................... 9
Front view .................................................................................................................................................................10

Oil supplies....................................................................................... 11
Axle oil (MTF) supply ...............................................................................................................................................11
Haldex oil supply ......................................................................................................................................................12
Oil deterioration .......................................................................................................................................................12
Changing the oil .......................................................................................................................................................12

All-wheel drive clutch....................................................................... 13
Oil supply, lubrication and clutch cooling .............................................................................................................13
Clutch control ...........................................................................................................................................................15

Cooling............................................................................................. 17
Cooling circuit ..........................................................................................................................................................17

Function diagram.............................................................................. 19
All Wheel Drive Control Module J492 .....................................................................................................................19

Sensors and actuators...................................................................... 20
All Wheel Drive Hydraulic Pressure Sensor G942 .................................................................................................20
All Wheel Drive Hydraulic Temperature Sensor G943 ..........................................................................................20
Haldex Clutch Pump V181 ......................................................................................................................................21

Audi drive select............................................................................... 22
Operating situations......................................................................... 23
Launch control program .........................................................................................................................................23
Torque vectoring ......................................................................................................................................................23

Service.............................................................................................. 25
Using the VAS Scan Tool .........................................................................................................................................25
Maintenance and change intervals ........................................................................................................................26
Towing ......................................................................................................................................................................26
Warning lights .........................................................................................................................................................26
Limp-home concept .................................................................................................................................................26

Knowledge assessment.................................................................... 27

This eSelf Study Program teaches a basic knowledge of the design and functions of new models,
new automotive components or technologies.
It is not a Repair Manual! All values given are intended as a guideline only.
For maintenance and repair work, always refer to the current technical literature.

Note

Reference

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1

Introduction
Front final drive 0D4
Front final drive 0D4 is being used in an Audi for the first
time with the 2017 R8. It is a key component of the newly
developed quattro powertrain for this vehicle.

Audi drive select allows the driver to control the all-wheel
drive clutch, and thus the distribution of torque and drive
power between the front and rear axles.

The quattro powertrain of the Audi R8 has the ability to
adapt drive output (depending on driving situation and
weather) to driving conditions, and to transfer up to 100%
of that output to the front or rear axle. This gives better
driving dynamics and improves driving stability.

In addition, the optional performance mode of Audi drive
select enables the all-wheel drive control module to be
adapted to "dry", "wet" and "snow" road conditions for the
first time. This means that the driver can configure the
all-wheel drive control module for extremely short reaction
times.

This distribution of drive torque or drive power is made
possible by the electro-hydraulically operated all-wheel
drive clutch in the final drive.

Final drive 0D4, in conjunction with Audi drive select,
7-speed dual clutch transmission 0BZ (S tronic) and the
high-performance 10-cylinder engines, enhances the Audi
R8 driving experience in terms of power transmission.

642_001

Learning objectives of this eSelf -Study Program:
This eSelf-Study program provides you with information
about front final drive 0D4. Once you have completed it you
will be able to answer the following questions:

›› How is front final drive 0D4 designed and how does it
work?
›› How do the software-assisted transmission functions
influence operation of the final drive and the vehicle?

2

System description
Final drive 0D4 and the 7-speed dual clutch transmission
0BZ provide the basis for the quattro powertrain of the
2017 Audi R8.
The vehicle is primarily driven through the rear axle. The
rear axle is able to transmit all available drive power, provided that a portion of the drive power is not transferred to
the front axle through the all-wheel drive clutch in the
front final drive.
To assist the active distribution of drive torque and drive
power, the mechanical limited slip differential of the rear
axle has been reconfigured.
The drive power for the front axle is transferred through the
transmission output shaft. The reduction ratio of the transmission output shaft is such that the circumferential speed
of the front wheels is slightly higher than the circumferential
speed of the rear wheels. This difference is referred to as
"lead". Depending on the driving situation, it is the basis for
the controlled transfer of up to 100% of drive torque (drive
power) to the front axle. Refer to page 6.

In a complex process, the all-wheel drive control module
decides how much torque is to be transferred. The torque
to be transmitted by the all-wheel drive clutch is controlled
by activation of the Haldex Clutch Pump V181. The allwheel drive control module also factors in the coefficients
of friction in the all-wheel drive clutch while making allowance for oil deterioration. The all-wheel drive control software and the programmed values for oil deterioration are
stored in All Wheel Drive Control Module J492.
The Audi drive select modes and approximately 130 different signals - including signals for ambient conditions, axle
load distribution, driver input, longitudinal acceleration,
yaw rate, transverse acceleration, steering angle, vehicle
speed, engine torque and gear ratio - are incorporated into
the all-wheel drive control process.
The distribution of drive power to the front and rear axles
has a significant influence on the traction, driving dynamics
and driving stability of the Audi R8. The positive effect of
the all-wheel drive clutch control module is explained on
page 5.

The all-wheel drive clutch of the newly developed front
final drive gets the torque for driving the front axle from
the transmission output shaft through the propeller shaft,
the central shaft and the all-wheel drive clutch input shaft.
At the same time, it transfers up to 406 lb ft (550 Nm) of
torque to the differential pinion shaft.

Selector mechanism

Front final drive 0D4

Central shaft

All Wheel Drive Control Module
J492
Refer to page 19

3

Rear axle limited slip differential

7-speed dual clutch transmission 0BZ

642_002

Propeller shaft
Spline for dual mass flywheel – transmission
input
Drive shaft

Transmission output shaft
›› Front final drive input shaft
›› PTO shaft (power take-off)

4

Distribution of drive power
The 10-cylinder engines of the Audi R8 have the ability to
deliver between 398 - 413 lb ft (540 - 560 Nm) of peak
torque to the transmission.

The 1106 lb ft (1500 Nm) of torque at the front axle corresponds to approximately 45% of drive power in 4th gear
and at full engine torque.

If the rear axle puts down its full drive power in 4th gear
and at peak engine torque, approximately 2213 lb ft
(3000 Nm) of torque is applied.

The extent to which the variable range of the all-wheel
drive clutch can influence the distribution of drive power
between the front and rear axles depends on the engine
torque and the driveline ratios.

Irrespective of the engine torque and selected gear, the
all-wheel drive clutch can transfer a portion of the available drive power in a controlled manner. In this way, up to
406 lb ft (550 Nm) of torque are transferred to the front
differential pinion shaft. Refer to page 11. The reduction ratio of the differential produces up to 1106 lb ft
(1500 Nm) of torque at the front axle.

Depending on the engine torque and selected gear, up to
100% of drive power can be transferred to the front axle
due to the front axle lead.

Front axle lead
The gear ratios of the driveline are such that the circumferential speed of the front wheels is slightly higher than the
circumferential speed of the rear wheels. This configuration
is referred to as "front axle lead". Due to this lead effect,
wheel speeds are continuously compensated in the allwheel drive clutch. The associated speed differential is the
basis for exact clutch control. The clutch is operated with
zero backlash. This permits very short reaction times during
closing of the clutch.

Longitudinal
force
Rear axle 80%

Front axle 20%

Lateral force

Longitudinal slip λ

Zero-backlash operation of the clutch results in a very small
amount of drag torque. Refer to page 9.
The speed compensation effect and the drag torque resulting from the lead of the front axle produce frictional heat in
the clutch. To dissipate the heat which is generated, the
clutch and the final drive are cooled from the radiator.
Refer to page 13 and page 17.
Depending on the engine torque and driveline ratios, the
front axle lead also allows more than 50% of drive power
to be transferred to the front axle, improving driving
dynamics and driving stability. Reducing the longitudinal
force on an axle allows the axle to absorb more lateral
force.
Initial scenario
This can be illustrated by an initial scenario where 20% of
drive power is transmitted to the front axle and 80% to the
rear axle in a controlled manner.
Conversely, the lateral force which can be transmitted by
the front axle is proportionately greater than the lateral
force which can be transmitted by the rear axle.
If the vehicle incurs critical oversteer in this situation, it
can be stabilized by transferring drive power towards the
front axle.

5

642_017

Stabilization without front axle lead
λ FA

λ RA

If a vehicle does not have front axle lead, that is, the front
and rear wheels spin at the same circumferential speed,
front axle drive power can be increased to a maximum of
50%, if necessary. If the rear axle transmits more torque
(drive power) than the front axle, there is more slip at the
rear wheels. Due to the greater amount of slip at the rear
wheels, wheel speeds are compensated in the all-wheel
drive clutch, allowing the torque of the all-wheel drive
clutch to be increased further. This is possible until the
front axle transmits the same amount of drive power as the
rear axle.

Longitudinal slip λ

Longitudinal
force

Rear axle 50%
Front axle 50%

Lateral force

Longitudinal slip λ

642_018

λ FA

λ RA

Longitudinal slip λ

Given that the front and rear wheels can have equal
amounts of slip, wheel speeds are not compensated in the
all-wheel drive clutch. It makes no sense to further increase
the pressure on the multi-plate clutch with plates rotating
at the same speed because it is not possible to transmit
more torque to the front axle.
Equal amounts of lateral force can be transmitted to the
front and rear axles. The lateral force which can be transmitted to the rear axle has increased compared to the
initial scenario. This counteracts oversteer.

Stabilization with front axle lead
Longitudinal
force

The lead of the front axle enables front axle drive power to
be increased to over 50%. Due to the lead of the front axle,
wheel speeds are compensated in the all-wheel drive clutch
even if the drive power split is 50/50. This allows the
amount of torque transferred to the front axle to be
increased further.

Front axle 70%

Rear axle 30%
Lateral force

Depending on the engine torque and gear ratio, up to 100%
of drive torque (drive power) is available to the front axle.

Longitudinal slip λ

λ FA

λ RA

Longitudinal slip λ

642_019

The amount of lateral force which can be transmitted by
the front axle is consequently less than the amount of
lateral force which can be transmitted by the rear axle. If
the vehicle incurs critical oversteer in this situation, it can
be stabilized much more effectively than a vehicle without
front axle lead.

6

Component overview
The component overview largely reflects the components
which can be replaced during repair work.

Cross-member bolt
Front final drive

Front cross-member for
front final drive
Bracket with rubber metal bearing,
bolted to body
Shaft oil seal

Splined flange shaft

Snap ring
Vent for all-wheel
drive clutch oil supply

Sealing surface, sealed
with liquid sealant

Outlet port for pressure
relief valve and vent port
for pump sump of Haldex
Clutch Pump V181

All-wheel drive
clutch
Pressure relief
valve

Final drive with
open differential
Final drive / differential vent

O-ring

Coolant connection

Cooling channel plate

O-ring
All Wheel Drive Hydraulic
Pressure Sensor G942

Three-point bearing

All Wheel Drive Hydraulic
Temperature Sensor G943

The final drive is connected to the vehicle body by a threepoint bearing. The front cross-member is held in place by
two brackets with rubber-metal bearings.
The elongated housing of the central shaft helps to support
the torque of the final drive. It is connected to the rear
cross-member of the final drive by a rubber-metal bearing.
A final drive which is not installed without pre-load can
cause vibration and noise. During repair work always refer
to the instructions in ElsaPro.

7

!

O-ring

O-rings

Haldex Clutch Pump V181 with
wiring connector for G942 and
G943

Note
If the "central shaft housing / all-wheel drive clutch / final drive" bolt is removed, the seal between the final drive and the
all-wheel drive clutch must be replaced with the liquid seal specified in the Electronic Parts Catalog (ETKA).

Installing the propeller shaft

The propeller shaft transmits drive torque to the central
shaft by means of a spline. A bellows prevents the ingress
of dirt and moisture into the spline. The bellows must be
properly installed as shown in the diagram. Follow the
installation instructions given in ElsaPro.

Bellows seal

Anti-dust ring
Ball bearing
Snap ring
Anti-dust ring

Retaining bead engages
groove

Rubber-metal bearing

"Central shaft housing / all-wheel drive
clutch / final drive" bolt
Propeller shaft

To help prevent imbalance, there is a colored mark on the
central shaft and on the propeller shaft. The two marks must
be matched up as closely as possible during assembly.

Bellows seal
Central shaft
housing

Propeller shaft

Central shaft

642_003

Front cross-member for
front final drive

8

Cutaway view of transmission
Longitudinal section A-A
Central shaft

Anti-dust ring

Central shaft housing

Snap ring
Ball bearing
Anti-dust ring

Rubber-metal
bearing

Multi-plate clutch

Zero-backlash clutch operation

Clutch piston with axial bearing

The all-wheel drive clutch is a multi-plate
clutch. A diaphragm spring presses the clutch
piston against the clutch plates, with the result
that the clutch is free of backlash. This permits
very short control times during closing of the
clutch. Zero-backlash operation results in a
small amount of drag torque if the clutch is not
activated. To dissipate the resultant frictional
heat, the clutch is cooled by the mechanical oil
pump. Refer to page 12.

Diaphragm spring

Pressure relief valve

Final drive / differential vent
Final drive with open differential