Drivetrain - Vibration/Humming From Transfer Case
SI B27 01 10Intermediate and Special Transmission
November 2010
Technical Service
SUBJECT
Vibration or Humming Noise from the Transfer Case While Driving
MODEL
E83 with M54 or N52K engines
SITUATION
The customer may report one or more of the following conditions:
^ A vibrating, humming noise and/or noise from the drivetrain when traveling at speeds of 50 mph and higher; this condition is particularly noticeable while coasting.
^ A grabbing/juddering or chattering condition under hard acceleration in low gears; in some cases, the customer may describe this as a slipping/slippage condition of the automatic transmission.
^ Vibrations when driving through curves at low speeds.
CAUSE
Non-approved wheels/tires can have variations in production tolerances which create deviations in the wheel speed signals. These deviations can result in unnecessary/erratic activation of the transfer case clutch. Continued driving with this condition present can lead to premature wear of the transfer case fluid.
PROCEDURE
When diagnosing customer complaints, proceed as follows:
1. Check the wheels and tires fitted to the vehicle. Ensure that an approved set of wheels and tires is installed. Reference KSD for approved wheel/tire combinations.
2. Check and adjust the tire pressures. Inspect the tread depth of the tires to determine whether the tires are worn and require replacement.
3. In cases where non-approved wheel/tire sets or worn tires are fitted, install a set of known good wheels and tires; then test drive the vehicle prior to any further diagnosis. If the condition has been eliminated, no further diagnosis is necessary. If the condition remains, proceed to step 4.
4. Drain and replace the transfer case fluid and reset the wear values in the VTG. Perform a test drive with a known good set of wheels and tires installed.
5. If the condition still exists, continue diagnosing mechanical components of the drive line.
NOTE
Do not replace the transfer case. If symptoms are no longer present after disconnecting the VTG actuator,the issue is related to the activation of the clutch housed within the VTG transfer case. This does not necessarily mean that the problem is in the transfer case. The issue may be resolved by replacing the transfer case in the short term. However, if the problem was originally related to the wheels/tires, then the symptoms will return within a short period of time. Therefore, the procedure listed above must be performed to properly diagnose this type of condition.
WARRANTY INFORMATION
For information only
Repairs required due to tire wear, size or non-approved tires are not covered under warranty.