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Chevrolet Silverado / GMC Sierra. Manual - part 2839
Mode block
3. Inspect the synchronizer sleeve or synchronizer hub for
being faulty.
4. Replace the synchronizer sleeve or synchronizer hub if it
is faulty. Refer to Transfer Case Assemble.
If the symptoms occur during cold temperatures, flush and fill
the front axle with synthetic fluid. Refer to Front Axle
Lubricant Level Inspection (9.25 Inch Axle) .
High/low shift fork
1. Inspect the high/low shift fork for the following
conditions:
The pin on the shift fork for wear or damage
Worn or melted range fork pads
Cracked or bent shift fork
Refer to High/Low Shift Components Cleaning
and Inspection .
2. Replace the following components if found faulty:
The shift fork pads
The shift fork
Refer to Transfer Case Disassemble and
Transfer Case Assemble .
High/low clutch
1. Inspect the high/low clutch for the following conditions:
Engagement teeth for burrs or damage
Sliding freely on the rear output shaft
The high/low clutch collar for excessive wear
Refer to High/Low Shift Components Cleaning
and Inspection .
2. Replace the high/low clutch if faulty. Refer to Transfer
Case Disassemble and Transfer Case Assemble.
1. Inspect for the following conditions:
Failed input shaft pilot bearing in the input shaft
Journal on the rear output shaft for excessive wear
2008 Chevrolet Silverado 1500
2008 TRANSMISSION Transfer Case - MP 1222/1225/1226-NQG - Cab & Chassis Sierra, Cab & Chassis Silverado,
Sierra & Silverado
TRANSFER CASE JUMPS OUT OF GEAR
Input shaft pilot bearing
assembly
or damage
Refer to Front Output Shaft and Input Shaft
Cleaning and Inspection and Rear Output Shaft
Cleaning and Inspection .
2. Replace the bearing if faulty. Refer to Input Shaft Pilot
Bearing Replacement (Light Duty) or Input Shaft
Pilot Bearing Replacement (Heavy Duty and Super
Heavy Duty).
3. Replace the rear output shaft if damaged. Refer to
Transfer Case Disassemble and Transfer Case
Assemble.
High/low planetary carrier
assembly
1. Inspect the high/low planetary engagement teeth for burrs
or damage. Refer to High/Low Planetary Carrier
Cleaning and Inspection.
2. Replace the high/low planetary carrier assembly if faulty.
Refer to Transfer Case Disassemble and Transfer
Case Assemble.
Cause
Correction
DEFINITION: Loss of the transfer case drive torque during deceleration, acceleration or
under load.
Review the Symptoms - Transfer Case and perform the necessary inspections.
Shift linkage worn
1. Inspect the shift linkage for correct adjustment or for
being worn.
2. Replace the faulty component. Refer to Transfer Case
Control Lever Replacement and Transfer Case
Control Rod Replacement.
High/low shift fork pads
1. Inspect the high/low shift fork pads for wear. Refer to
High/Low Shift Components Cleaning and
Inspection.
2. Replace the fork pads if worn. Refer to Transfer Case
Disassemble and Transfer Case Assemble.
1. Inspect the high/low shift fork for being damaged. Refer
2008 Chevrolet Silverado 1500
2008 TRANSMISSION Transfer Case - MP 1222/1225/1226-NQG - Cab & Chassis Sierra, Cab & Chassis Silverado,
Sierra & Silverado
Faulty high/low shift fork
to High/Low Shift Components Cleaning and
Inspection.
2. Replace the shift fork if faulty. Refer to Transfer Case
Disassemble and Transfer Case Assemble.
Faulty high speed teeth on
the high/low clutch
1. Inspect for the following conditions:
The input shaft high speed engagement teeth for
wear or damage
The engagement teeth on the high/low clutch for
wear or damage
Refer to Front Output Shaft and Input Shaft
Cleaning and Inspection and High/Low Shift
Components Cleaning and Inspection .
2. Replace the high/low clutch if the teeth are faulty. Refer
to Transfer Case Disassemble and Transfer Case
Assemble.
3. Replace the input shaft if the engagement teeth are faulty.
Refer to Transfer Case Disassemble and Transfer
Case Assemble.
Faulty control actuator shaft
1. Inspect the control actuator shaft for wear. Refer to
High/Low Shift Components Cleaning and
Inspection.
2. Replace the control actuator shaft if faulty. Refer to
Transfer Case Disassemble and Transfer Case
Assemble.
High/low planetary carrier
assembly
1. Inspect the high/low planetary carrier for the following
conditions:
Low speed engagement teeth worn or damaged
Cracked carrier housing
Planetary gear needle bearings worn
Planetary gears broken or damaged teeth
Planetary gears seized or binding
Refer to High/Low Planetary Carrier Cleaning
and Inspection .
2008 Chevrolet Silverado 1500
2008 TRANSMISSION Transfer Case - MP 1222/1225/1226-NQG - Cab & Chassis Sierra, Cab & Chassis Silverado,
Sierra & Silverado
TRANSFER CASE LEAK DIAGNOSIS
2. Replace the high/low planetary carrier if any of the
above conditions exist. Refer to Transfer Case
Disassemble and Transfer Case Assemble.
Front output shaft drive
sprocket
1. Inspect the drive sprocket for worn engagement teeth.
Refer to Drive Chain, Drive Sprocket, and Driven
Sprocket Cleaning and Inspection.
2. Replace the drive sprocket if faulty. Refer to Transfer
Case Disassemble and Transfer Case Assemble.
2/4 wheel drive
synchronizer sleeve
1. Inspect the synchronizer sleeve for worn engagement
teeth. Refer to Two/Four Wheel Drive Shift
Components Cleaning and Inspection.
2. Replace the synchronizer sleeve if faulty. Refer to
Transfer Case Disassemble and Transfer Case
Assemble.
Cause
Correction
DEFINITION: A visible indication of an external fluid leak from the transfer case.
Review the Symptoms - Transfer Case and perform the necessary inspections.
Drain plug or fill plug leak
1. Inspect for the correct sealer and the correct amount of
sealer on the plugs. Refer to Sealers, Adhesives, and
Lubricants.
2. Install the plugs correctly. Refer to Transfer Case Fluid
Replacement.
Access hole plugs leaking
Replace the access hole plugs or seal with room temperature
vulcanizing (RTV) sealer.
Vehicle speed sensor (VSS)
leaking
1. Remove the VSS. Refer to Vehicle Speed Sensor
Replacement.
2. Inspect the VSS for the following conditions:
Cross threaded
Cut or damaged VSS O-ring seal
VSS over tightened causing deformation in the VSS
3. Replace the VSS O-ring seal if faulty.
4. Replace the VSS if faulty.
2008 Chevrolet Silverado 1500
2008 TRANSMISSION Transfer Case - MP 1222/1225/1226-NQG - Cab & Chassis Sierra, Cab & Chassis Silverado,
Sierra & Silverado
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