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Chevrolet Silverado / GMC Sierra. Manual - part 2930
TRANSFER CASE LEAK DIAGNOSIS
3. Replace the input shaft if the engagement teeth are 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 .
2. Replace the high/low planetary carrier if any of the
above conditions exist. Refer to Transfer Case
Disassemble and Transfer Case Assemble.
Input shaft pilot bearing
assembly
1. Inspect the bearing in the input shaft and the rear output
shaft journal for excessive wear. Refer to Front Output
Shaft and Input Shaft Cleaning and Inspection and
Rear Output Shaft Cleaning and Inspection
.
2. Replace the bearing and the rear output shaft if faulty.
Refer to Input Shaft Pilot Bearing Replacement
(Light Duty) or Input Shaft Pilot Bearing
Replacement (Heavy Duty and Super Heavy Duty)
and Transfer Case Assemble.
Input shaft
1. Inspect the input shaft for broken or damaged teeth.
Refer to Front Output Shaft and Input Shaft
Cleaning and Inspection.
2. Replace the input shaft 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.
2008 Chevrolet Silverado 1500
2008 TRANSMISSION Transfer Case - MP 3023/3024-NQH - Cab & Chassis Sierra, Cab & Chassis Silverado, Sierra &
Silverado
Review the Symptoms - Transfer Case and perform the necessary inspections.
Drain plug or fill plug leak
1. Inspect for the correct sealer and amount of sealer on the
plugs. Refer to Sealers, Adhesives, and Lubricants.
2. Correctly install the plugs. Refer to Transfer Case
Fluid Replacement.
Access hole plugs leaking
Replace the access hole plugs or seal with room temperature
vulcanizing (RTV) sealant.
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.
Rear output shaft seal
leaking
1. Inspect for the following conditions:
Overfilled or improper transfer case fluid
Blocked vent
Seal improperly installed, worn, or damaged
Seal bore damaged or cracked
Rear output shaft bushing for excessive wear
Slip yoke seal surface for wear or pitting
2. Repair or replace the following components if found
faulty:
Adjust or replace the transfer case fluid. Refer to
Transfer Case Fluid Replacement .
Clean or properly route the vent hose.
Replace the rear output shaft seal. Refer to Rear
Output Shaft Seal Replacement .
Replace the rear case half if the seal bore is
damaged. Refer to Transfer Case Disassemble
and Transfer Case Assemble .
Replace the rear bushing if worn. Refer to
Transfer Case Rear Extension Bushing
2008 Chevrolet Silverado 1500
2008 TRANSMISSION Transfer Case - MP 3023/3024-NQH - Cab & Chassis Sierra, Cab & Chassis Silverado, Sierra &
Silverado
Replacement .
Replace the slip yoke if the surface could cause
leakage. Refer to One-Piece Propeller Shaft
Replacement or Two-Piece Propeller Shaft
Replacement .
Front output shaft seal
leaking
1. Inspect for the following conditions:
Overfilled or improper transfer case fluid
Blocked vent
Seal improperly installed, worn or damaged
Seal bore damaged or cracked
Leaking cup plug in the front output shaft
2. Repair or replace the following components if found
faulty:
Adjust or replace the transfer case fluid. Refer to
Transfer Case Fluid Replacement .
Clean or properly route the vent hose.
Replace the front output shaft seal. Refer to Front
Output Shaft Seal Replacement .
Replace the front case half if the seal bore is
damaged. Refer to Transfer Case Disassemble
and Transfer Case Assemble .
Replace the cup plug in the front output shaft if it is
leaking. Refer to Transfer Case Disassemble and
Transfer Case Assemble .
2/4 wheel drive actuator
seal leaking
Replace the actuator seal. Refer to Transfer Case Two/Four
Wheel Drive Actuator Replacement.
Leaking at the vent pipe
Transfer case overfilled
Inspect for the correct transfer case fluid level. Refer to
Transfer Case Fluid Replacement.
Inspect for a damaged or missing vent pipe.
Replace a damaged or missing vent and seal the vent pipe
with the correct sealer. Refer to Transfer Case
Assemble.
2008 Chevrolet Silverado 1500
2008 TRANSMISSION Transfer Case - MP 3023/3024-NQH - Cab & Chassis Sierra, Cab & Chassis Silverado, Sierra &
Silverado
REPAIR INSTRUCTIONS - ON VEHICLE
TRANSFER CASE SHIFT CONTROL SWITCH REPLACEMENT (WITHOUT SLT)
Transfer case to adapter
leak
1. Inspect for the following conditions:
Loose mounting fasteners
Gasket faulty
The transfer case input shaft seal leaking
The pilot bearing in the input shaft leaking
2. Repair or replace the following components if found
faulty:
Repair or replace the loose fasteners. Refer to
Transfer Case Adapter Replacement .
Replace the transfer case adapter gasket. Refer to
Transfer Case Adapter Replacement .
Replace the transfer case input shaft seal. Refer to
Input Shaft Seal Replacement .
Inspect for the following conditions:
Seal improperly installed, worn, or damaged
Seal bore damaged or cracked
Input shaft seal surface worn, grooved, or
damaged
Replace the pilot bearing in the input shaft if it is
leaking. Refer to Transfer Case Disassemble and
Transfer Case Assemble .
Case leaking
1. Inspect for the following conditions:
A cracked case
Case porosity
2. Replace the faulty case half. Refer to Transfer Case
Disassemble and Transfer Case Assemble.
Front case half to rear case
half seam leak
Disassemble and seal the case halves. 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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