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Chevrolet Silverado / GMC Sierra. Manual - part 2927
Diagnostic Procedure Instructions provides an overview of each diagnostic category.
Circuit/System Description
If the service indicator needs to be turned on the transfer case shift control module sends a signal
via LAN to the instrument panel asking the I/P to command the Service 4WD indicator.
Reference Information
Schematic Reference
Transfer Case Control Schematics
Connector End View Reference
Component Connector End Views
Electrical Information Reference
Circuit Testing
Connector Repairs
Testing for Intermittent Conditions and Poor Connections
Wiring Repairs
Scan Tool Reference
Scan Tool Data List
Scan Tool Data Definitions
Circuit/System Testing
1. If the Service 4WD indicator is on and there are no DTCs check the fuse for the transfer
case as this would cause the transfer case control module to drop off the LAN causing a
service indicator.
2. If the fuse is good check the module power and grounds for proper connections as this could
cause the same thing as a blown fuse.
3. If this checks OK then check all other U codes that may be set against the transfer case shift
control module such as I/P, BCM, PCM, and follow the proper U code diagnostic.
Repair Procedures
2008 Chevrolet Silverado 1500
2008 TRANSMISSION Transfer Case - MP 3023/3024-NQH - Cab & Chassis Sierra, Cab & Chassis Silverado, Sierra &
Silverado
Perform the Diagnostic Repair Verification after completing the diagnostic procedure.
Control Module References for TCSCM replacement, setup, and programming
Transfer Case High/Low Clutch Reset
TRANSFER CASE HIGH/LOW CLUTCH RESET
Using a Scan Tool
1. Turn the ignition on go to the special functions heading in the scan tool.
2. Select Clutch Reset Procedure (Motor Learn Procedure).
3. When the Clutch Reset Procedure is initiated you should hear the motor engage, indicating a
successful learn procedure.
Using The Transfer Case Shift Control Switch
1. Turn the ignition to accessory, place the switch into the 2 high mode.
2. Turn the switch clockwise past 4 low into the neutral request mode and hold for 30 seconds.
3. An audible noise from the motor should occur indicating a successful learn procedure.
TRANSFER CASE POPPING NOISE
TRANSFER CASE WHINE OR RUMBLE NOISE
Cause
Correction
DEFINITION: A faulty internal transfer case component that causes a popping noise in the
transfer case.
Review the Symptoms - Transfer Case and perform the necessary inspections.
Chain jump
Replace the chain and sprockets. Refer to Transfer Case
Disassemble and Transfer Case Assemble.
Replace the shaft bearings. Refer to Transfer Case
Disassemble and Transfer Case Assemble.
Inspect for damaged components caused by metal debris.
Refer to Drive Chain, Drive Sprocket, and Driven
Sprocket Cleaning and Inspection and Front Output
Shaft and Input Shaft Cleaning and Inspection.
Cause
Correction
DEFINITION: A faulty internal transfer case component that causes a whine or rumbling
2008 Chevrolet Silverado 1500
2008 TRANSMISSION Transfer Case - MP 3023/3024-NQH - Cab & Chassis Sierra, Cab & Chassis Silverado, Sierra &
Silverado
TRANSFER CASE GROWL OR GRINDING NOISE
noise in the transfer case.
Review the Symptoms - Transfer Case and perform the necessary inspections.
Faulty bearings
1. Inspect all of the bearings and journals. Refer to Rear
Output Shaft Cleaning and Inspection, Front
Output Shaft and Input Shaft Cleaning and
Inspection, and Drive Chain, Drive Sprocket, and
Driven Sprocket Cleaning and Inspection.
2. Replace any faulty bearings, and any components with
faulty bearing journals. Refer to Transfer Case
Disassemble and Transfer Case Assemble.
Cause
Correction
DEFINITION: A faulty internal transfer case component that causes a growl or grinding
noise in the transfer case while the vehicle is turning or in a four wheel drive mode.
Review the Symptoms - Transfer Case and perform the necessary inspections.
High/low planetary carrier
assembly
1. Inspect the high/low planetary carrier assembly for the
following conditions:
Chipped, bent, or deformed teeth
Planetary gear needle bearings worn
Planetary gear thrust washers cracked or missing
Seized or binding planetary gears
Refer to High/Low Planetary Carrier Cleaning
and Inspection .
2. Replace the high/low planetary carrier assembly if any of
the above conditions exist. Refer to Transfer Case
Disassemble and Transfer Case Assemble.
1. Inspect the input shaft in the planetary carrier assembly
for excessive thrust end play.
2. Inspect the input shaft teeth for the following conditions:
Damage
Worn or galled thrust surfaces
Excessive wear
2008 Chevrolet Silverado 1500
2008 TRANSMISSION Transfer Case - MP 3023/3024-NQH - Cab & Chassis Sierra, Cab & Chassis Silverado, Sierra &
Silverado
TRANSFER CASE GRATING NOISE
Input shaft
Chipped teeth
Metal embedded in the root of the teeth
Refer to Front Output Shaft and Input Shaft
Cleaning and Inspection .
3. Replace the input shaft if faulty. Refer to Transfer Case
Disassemble and Transfer Case Assemble.
Thrust washers
1. Inspect for missing or damaged input shaft thrust washers.
2. Inspect the thrust washers for galling.
3. Replace the thrust washers if faulty and the mating
component if damaged. Refer to Transfer Case
Disassemble and Transfer Case Assemble.
High/low internal gear
1. Inspect the high/low internal gear teeth for the following
conditions:
Damage
Chipped teeth
Excessive wear
Metal embedded in the root of the teeth
Refer to Transfer Case Front Half Cleaning and
Inspection .
2. Replace the front case half if the high/low internal gear is
faulty. Refer to Transfer Case Disassemble and
Transfer Case Assemble.
Cause
Correction
DEFINITION: A faulty internal transfer case component that causes a grating noise in the
transfer case while in the AWD, 4HI, or 4LO mode.
Review the Symptoms - Transfer Case and perform the necessary inspections.
Broken clutch apply plate
1. Inspect for a broken clutch apply plate. Refer to
Transfer Case Disassemble and Transfer Case
Assemble.
2008 Chevrolet Silverado 1500
2008 TRANSMISSION Transfer Case - MP 3023/3024-NQH - Cab & Chassis Sierra, Cab & Chassis Silverado, Sierra &
Silverado
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