Some four-wheel drive 2020-2022 Silverado 2500HD/3500HD and Sierra 2500HD/3500HD trucks equipped with the 10-speed automatic transmission (MGM, MGU) and transfer case MP 3023/2024 (RPO NQH) may have a Service 4WD message displayed on the Driver Information Center (DIC). DTC C119E symptom 5A (Range Actuator System Performance) also be may be set in the Transfer Case Control Module (TCCM).
If unable to duplicate these conditions, which may not reset on a test drive, and there are not any other transfer case-related DTCs set, ask the customer if the DIC message displayed after an ABS event while in 4WD HI. If the customer does not know, drive the vehicle in 4WD HI in conditions where an ABS activation can be duplicated safely in order to try to repeat the condition. It may take several ABS events to reproduce the condition.
If the condition can been duplicated, use GDS to look at the transfer case data – under the Engineering Data 3 list – and record the transfer case clutch high value and low value on the repair order.
If the transfer case clutch high value is above 5 degrees, follow the diagnostic information in the appropriate Service Information.
If the transfer case clutch high value is below 5 degrees, remove the transfer case (Fig. 14) in order to replace a clutch shim. Refer to Transfer Case Assembly Replacement (with MGM, MGU Automatic Transmission) in the appropriate Service Information.
Fig. 14
TIP: Disassemble the transfer case using the appropriate procedure to gain access to the clutch pack assembly. Do not take apart the clutch pack assembly any farther than needed to access the necessary shim.
After removing the four-wheel-drive clutch housing (Fig. 15, #1), front output shaft driven sprocket spacer (Fig. 15, #2) and two/four-wheel-drive clutch retaining ring (Fig. 15, #3), remove the four-wheel drive clutch shim (Fig. 15, #4), measure it, and then replace it with the next smaller shim. For example, a removed shim that is 4.8 mm should be replaced with a 4.6 mm shim. Do not use the tool listed in the service document in Service Information to measure the clutch pack shim for this repair.
Fig. 15
After installing the smaller shim, reassemble and reinstall the transfer case. Perform the Transfer Case Range Actuator Learn procedure and then verify the high clutch value. Under the Engineering Data 3 list, the high clutch value should increase by 10–12*.
– Thanks to Steve Schipansky
