Rattle Noise at Highway Speed in 2WD or DTC C0327 - keywords 246 2hi 2high 2wd 4wd auto awd buzz case click indicator knock lamp light service tick transfercase trans vibration

The following diagnosis might be helpful if the vehicle exhibits the symptom(s) described in this PI.

Rattle noise from under the vehicle in 2WD only at approximately 60-65 mph and above. The noise will go away when shifted to either auto or 4WD hi. The noise can be duplicated with the vehicle on a hoist. The noise will be heard from the transfer case using a stethoscope or chassis ears. Vehicles involved were built approximately between 01/01/04 and 03/06/06. The rattle condition if not noticed by the customer may cause eventual encoder sensor wear causing DTC C0327 set in the Transfer Case Control Module (TCCM).

An updated TCCM calibration has been released to apply light pressure to the transfer case clutch pack and reduce the rattle. The calibration is scheduled for release on 3/18/07 and the title line will read "to correct transfer case rattle at highway speeds and possible DTC C0327". For Rattle only (no current DTC C0327 set), Install the updated calibration and if necessary follow the diagnostics listed below.

If the vehicle has a current or history dtc C0327 and can be diagnosed to the encoder sensor, re-flash with the updated calibrations and replace the encoder sensor as necessary.

Important note: All NV246 transfer cases built 02/25/06 and beyond are manufactured with pressed fit parts to help reduce the rattle. Inspect the ID tag on the transfer case for this build date and verify the tccm has the latest calibration before repairs are initiated.

Please follow this diagnostic or repair process thoroughly and complete each step. If the condition exhibited is resolved without completing every step, the remaining steps do not need to be performed.