Diagnostic Manual, Chassis and Drivetrain,
Volume 2
| LOCATION: |
8.1 4MATIC > 43 Mechanical Test Program - Frictional Torque Test |
Mechanical Test Program - Frictional Torque Test
Test step
DTC |
Test scope
|
Test connection
|
Test condition
|
Nominal value
|
Possible cause/Remedy
|
1.0
only vehicles up to 04/91 |
Front axle drivetrain multi-disc clutch (AV)
Preload
|
|
N30/3
Torque wrench
(15 - 65 Nm) |
|
Ignition: OFF
Unplug 4MATIC control module.
Selector lever in N position.
Engine: at idle
(allow to idle for approx. 30 sec., then shut off)
Place torque wrench on rear wheel and turn 90° in driving direction and read frictional torque. (Figure 1)
|
20 - 70 Nm
Note:
Excessive preload causes roughness while turning curves in shift stage 0. Insufficient preload delays the front axle drivetrain engagement time. |
Check that brakes are released if frictional torque is > 70 Nm.
Check for transfer case leakage.
Repair or replace transfer case as necessary.
34  4.0 |
| 2.0 |
Central differential lock multi-disc clutch (ZS)
Release process |
|
N30/3
Insert all 3 bridges simultaneously (Fig. 3)
Torque wrench
(15 - 65 Nm)
|
|
Ignition: OFF
Unplug 4MATIC control module (N30/3).
Selector lever in N position.
Engine: at idle
Place torque wrench on rear wheel and turn 90 ° in driving direction and read frictional torque. (Figure 1)
|
< 20 Nm |
Check that brakes are released if frictional torque is > 20 Nm.
Check for transfer case leakage.
Repair or replace transfer case as necessary.
Only vehicles up to 04/91:
 34 4.0 |
| 3.0 |
Rear axle differential lock multi-disc clutch (HS)
Measure frictional torque without engagement |
|
Torque wrench
(15 - 65 Nm) |
|
Lift rear of vehicle on one side.
Place torque wrench on rear wheel and turn 90 ° in driving direction and read and note frictional torque. (Figure 1)
|
see 3.1 |
3.1
|
| 3.1 |
Measure frictional torque with engagement |
|
N30/3
Torque wrench
(80 - 260 Nm)
|
|
Ignition: OFF
Unplug 4MATIC control module (N30/3).
Turn wheel back to position started from in step 3.0.
Engine: at idle
measure frictional torque through 90 ° and note value obtained (Figure 2) |
measured frictional torque from 3.1
minus
measured frictional torque from 3.0
> 100 Nm.
|
Difference < 100 Nm: Rear axle center piece. |
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Printable version
