Chevrolet Silverado / GMC Sierra. Service manual — part 2840

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

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
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 .

2008 Chevrolet Silverado 1500

2008 TRANSMISSION Transfer Case - MP 1222/1225/1226-NQG - Cab & Chassis Sierra, Cab & Chassis Silverado,

Sierra & Silverado

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
leaking. Refer to Transfer Case Disassemble and
Transfer Case Assemble .

Shift lever seal leaking

Replace the shift lever seal. Refer to Transfer Case
Disassemble and Transfer Case Assemble.

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 pipe and seal the vent
pipe with the correct sealer. Refer to Transfer Case
Assemble.

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

2008 Chevrolet Silverado 1500

2008 TRANSMISSION Transfer Case - MP 1222/1225/1226-NQG - Cab & Chassis Sierra, Cab & Chassis Silverado,

Sierra & Silverado

REPAIR INSTRUCTIONS - ON VEHICLE

TRANSFER CASE CONTROL LEVER REPLACEMENT

Fig. 4: Transfer Case Control Lever
Courtesy of GENERAL MOTORS CORP.

Seal bore damaged or cracked

Input shaft seal surface worn, grooved, or
damaged

Replace the pilot bearing in the input shaft if
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 1222/1225/1226-NQG - Cab & Chassis Sierra, Cab & Chassis Silverado,

Sierra & Silverado