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Transfer Case - Bw 4473-np3 Chevrolet Chevy Express G3500

Transfer Case 10 illustrations ~2710 words

Fastener Tightening Specifications

ApplicationSpecification
MetricEnglish
Adapter Bolts to Transmission50 N.m37 lb ft
Adapter Studs31 N.m23 lb ft
Drain Plug25 N.m18 lb ft
Fill Plug25 N.m18 lb ft
Mounting Nuts to Transfer Case50 N.m37 lb ft
Vehicle Speed Sensors17 N.m13 lb ft
Vent6 N.m53 lb in

Fastener Tightening Specifications

Capacities - Approximate Fluid

ApplicationSpecification
MetricEnglish
DEXRON®lll Fluid GM P/N 12346143 (Canadian P/N 10952622)1.4 liters1.5 quarts

Capacities - Approximate Fluid

Sealers, Adhesives, and Lubricants

ApplicationType of MaterialGM Part Number
United StatesCanada
Drain PlugPipe Sealant1234600410953480
Fill PlugPipe Sealant1234600410953480
Rear Case Half to Front Case HalfRTV Sealant1234573910953541
Vehicle Speed Sensor O-ringTransfer Case Fluid1234614310952622
VentPipe Sealant1234600410953480

Sealers, Adhesives, And Lubricants

Diagnostic Starting Point - Transfer Case

Begin the system diagnosis by reviewing the Symptoms - Transfer Case . The Symptoms - Transfer Case will provide the following information

  1. The required visual/physical inspections
  2. The list of symptoms

Use the Strategy Based Diagnosis in General Information in order to identify the correct procedure for diagnosing the system.

Strategy Based Diagnostics

Review the system operation in order to familiarize yourself with the system functions. Refer to Transfer Case Description and Operation .

Visual/Physical Inspection

  1. Inspect the easily accessible or visible system components for obvious damage, or for conditions which could cause the symptom.
  2. Inspect the transfer case for the proper fluid. Refer to «Transfer Case Fluid Replacement»(/chevrolet/chevy-express-g3500/1996-2012/remont/transfer-case/#transfer-case-bw-4473-np3) .

Symptom List

Refer to a symptom diagnostic procedure from the following list in order to diagnose the symptom

  1. «Transfer Case Popping Noise»(/chevrolet/chevy-express-g3500/1996-2012/remont/transfer-case/#transfer-case-bw-4473-np3__transfer-case-popping-noise)
  2. «Transfer Case Whine or Rumble Noise»(/chevrolet/chevy-express-g3500/1996-2012/remont/transfer-case/#transfer-case-bw-4473-np3__transfer-case-whine-or-rumble-noise)
  3. «Transfer Case Growl or Grinding Noise»(/chevrolet/chevy-express-g3500/1996-2012/remont/transfer-case/#transfer-case-bw-4473-np3__transfer-case-growl-or-grinding-noise)
  4. «Transfer Case Clunk during Acceleration and Deceleration»(/chevrolet/chevy-express-g3500/1996-2012/remont/transfer-case/#transfer-case-bw-4473-np3__transfer-case-clunk-during-acceleration-and)
  5. «Transfer Case No Front Drive»(/chevrolet/chevy-express-g3500/1996-2012/remont/transfer-case/#transfer-case-bw-4473-np3__transfer-case-no-front-drive)
  6. «Transfer Case Leak Diagnosis»(/chevrolet/chevy-express-g3500/1996-2012/remont/transfer-case/#transfer-case-bw-4473-np3__transfer-case-leak-diagnosis)
  7. «Transfer Case Viscous Coupling Test»(/chevrolet/chevy-express-g3500/1996-2012/remont/transfer-case/#transfer-case-bw-4473-np3__transfer-case-viscous-coupling-test)

Transfer Case Popping Noise

CauseCorrection
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 jumpReplace the chain and sprockets. Refer to Transfer Case Disassemble and Transfer Case Assemble in Transfer Case - BW 4473-NP3 Unit Repair. Replace the shaft bearings. Refer to Transfer Case Disassemble and Transfer Case Assemble in Transfer Case - BW 4473-NP3 Unit Repair. Inspect for damaged components caused by metal debris. Refer to Cleaning and Inspection in Transfer Case - BW 4473-NP3 Unit Repair.

Transfer Case Popping Noise

Transfer Case Whine or Rumble Noise

CauseCorrection
DEFINITION: A faulty internal transfer case component that causes a whine or rumble noise in the transfer case. Review the Symptoms - Transfer Case and perform the necessary inspections.
Faulty bearingsInspect all of the bearings and journals. Refer to Cleaning and Inspection in Transfer Case - BW 4473-NP3 Unit Repair. Replace any faulty bearings, and any components with faulty bearing journals. Refer to Transfer Case Disassemble and Transfer Case Assemble in Transfer Case - BW 4473-NP3 Unit Repair.

Transfer Case Whine Or Rumble Noise

Transfer Case Growl or Grinding Noise

CauseCorrection
DEFINITION: A faulty internal transfer case component that causes a growl or grinding noise from the transfer case. Review the Symptoms - Transfer Case and perform the necessary inspections.
Planetary carrierInspect the planetary carrier pinion gears for the following conditions: Chipped, bent or deformed teeth Pinion gear bushings worn Pinion gear thrust washers missing Seized or binding pinion gears Refer to Cleaning and Inspection in Transfer Case - BW 4473-NP3 Unit Repair. Inspect the planetary carrier for deformation. Refer to Cleaning and Inspection in Transfer Case - BW 4473-NP3 Unit Repair. Replace the planetary carrier assembly if faulty. Refer to Transfer Case Disassemble and Transfer Case Assemble in Transfer Case - BW 4473-NP3 Unit Repair.
Annulus gearInspect the annulus gear for teeth damage or wear. Refer to Cleaning and Inspection in Transfer Case - BW 4473-NP3 Unit Repair. Replace the annulus gear if faulty. Refer to Transfer Case Disassemble and Transfer Case Assemble in Transfer Case - BW 4473-NP3 Unit Repair.
Sun gearInspect the sun gear for the following conditions: Gear tooth failure Worn or galled thrust surfaces Refer to Cleaning and Inspection in Transfer Case - BW 4473-NP3 Unit Repair. Replace the sun gear if faulty. Refer to Transfer Case Disassemble and Transfer Case Assemble in Transfer Case - BW 4473-NP3 Unit Repair.
Thrust washersInspect the thrust washers for seizure to the planetary carrier. Inspect the thrust washers for galling. Replace the thrust washers if faulty and the mating component if damaged. Refer to Transfer Case Disassemble and Transfer Case Assemble in Transfer Case - BW 4473-NP3 Unit Repair.

Transfer Case Growl Or Grinding Noise

Transfer Case Clunk during Acceleration and Deceleration

CauseCorrection
DEFINITION: During acceleration or deceleration, a clunk is heard or felt in the transfer case. Review the Symptoms - Transfer Case and perform the necessary inspections.
Incorrect fluid level or incorrect fluidInspect the transfer case for the correct fluid level. Refer to Transfer Case Fluid Replacement . Inspect the transfer case for the correct type of fluid. Flush the transfer case and fill with the correct fluid, if required. Refer to Transfer Case Fluid Replacement .
Excessive clearance between the slip yoke and the rear output shaftInspect for the following conditions: Worn slip yoke splines Worn rear output shaft splines Repair or replace the following components if faulty. Replace the slip yoke, if required. Refer to Propeller Shaft Replacement - One Piece or Propeller Shaft Replacement - Two Piece in Propeller Shaft. Replace the rear output shaft, if required. Refer to Transfer Case Disassemble and Transfer Case Assemble in Transfer Case - BW 4473-NP3 Unit Repair.
Excessive clearance between the slip yoke and the rear bushingInspect for the following conditions: Worn rear bushing Worn slip yoke bushing journal Repair or replace the following components if faulty. Replace the slip yoke, if required. Refer to Propeller Shaft Replacement - One Piece or Propeller Shaft Replacement - Two Piece in Propeller Shaft. Replace the rear case half if the rear bushing is worn. Refer to Transfer Case Assemble in Transfer Case - BW 4473-NP3 Unit Repair.
Worn or faulty planetary carrierInspect the planetary carrier for the following conditions: Worn annulus gear Worn or faulty pinion gears Loose pinion gears Planetary carrier to mainshaft splines for wear Refer to Cleaning and Inspection in Transfer Case - BW 4473-NP3 Unit Repair. Replace the planetary carrier assembly and annulus gear if faulty. Refer to Transfer Case Disassemble and Transfer Case Assemble in Transfer Case - BW 4473-NP3 Unit Repair.
Worn or missing sun gear thrust washersInspect to ensure the thrust washers are installed. Inspect the thrust washers and mating surface for excessive wear. Replace the worn or missing thrust washers. Refer to Transfer Case Disassemble and Transfer Case Assemble in Transfer Case - BW 4473-NP3 Unit Repair.
Worn or damaged sun gearInspect the sun gear external gear teeth for excessive wear. Replace the sun gear or rear output shaft if worn. Refer to Transfer Case Disassemble and Transfer Case Assemble in Transfer Case - BW 4473-NP3 Unit Repair.
Rear output shaft bearing outer retaining ringInspect for the following conditions: Proper installation of the rear output shaft bearing retaining ring Excessive wear or damage to the retaining ring groove in the rear case half Repair or replace the following components if found faulty. Refer to Transfer Case Disassemble and Transfer Case Assemble in Transfer Case - BW 4473-NP3 Unit Repair. Properly install a new rear output shaft bearing outer retaining ring. Replace the rear case half if the retaining ring groove is excessively worn.

Transfer Case Clunk during Acceleration And Deceleration

Transfer Case No Front Drive

CauseCorrection
DEFINITION: The transfer case is not delivering engine torque to the front propeller shaft. Review the Symptoms - Transfer Case and perform the necessary inspections.
Viscous coupling faultyInspect the transfer case fluid for being black. If the fluid is black, it is most likely caused by a viscous coupling failure. Test for a faulty viscous coupling. Refer to Transfer Case Viscous Coupling Test . Disassemble the transfer case. Refer to Transfer Case Disassemble in Transfer Case - BW 4473-NP3 Unit Repair. Inspect the viscous coupling for leaking. Refer to Cleaning and Inspection in Transfer Case - BW 4473-NP3 Unit Repair. Replace the viscous coupling if it is faulty. Refer to Transfer Case Assemble in Transfer Case - BW 4473-NP3 Unit Repair.
Planetary carrier faultyDisassemble the transfer case. Refer to Transfer Case Disassemble in Transfer Case - BW 4473-NP3 Unit Repair. Inspect for faulty planetary carrier components. Refer to Cleaning and Inspection in Transfer Case - BW 4473-NP3 Unit Repair. Replace any faulty planetary carrier components. Refer to Transfer Case Assemble in Transfer Case - BW 4473-NP3 Unit Repair.

Transfer Case No Front Drive

Transfer Case Leak Diagnosis

CauseCorrection
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 leakInspect for the correct sealer and amount of sealer on the plugs. Correctly install the plugs. Refer to Transfer Case Fluid Replacement .
Vehicle speed sensor leakingRemove the vehicle speed sensor (VSS) and inspect for the following conditions: Cross threaded Cut or damaged O-ring seal VSS over tightened causing deformation in the VSS Refer to Transfer Case Speed Sensor Replacement . Replace the VSS O-ring seal if faulty. Refer to Transfer Case Speed Sensor Replacement . Replace the VSS if faulty. Refer to Transfer Case Speed Sensor Replacement .
Rear output shaft seal leakingInspect 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 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 slip yoke if the surface could cause leakage. Refer to Propeller Shaft Replacement - One Piece and Propeller Shaft Replacement - Two Piece in Propeller Shaft. Replace the rear case half if the rear bushing is worn. Refer to Transfer Case Disassemble and Transfer Case Assemble in Transfer Case - BW 4473-NP3 Unit Repair. Replace the rear case half if the seal bore is damaged. Refer to Transfer Case Disassemble and Transfer Case Assemble in Transfer Case - BW 4473-NP3 Unit Repair. Replace the rear output shaft seal. Refer to Transfer Case Output Shaft Seal Replacement - Rear .
Front output shaft seal leakingInspect for the following conditions: Overfilled or improper transfer case fluid Blocked vent Seal improperly installed, worn or damaged Seal bore damaged or cracked 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 case half if the seal bore is damaged. Refer to Transfer Case Disassemble and Transfer Case Assemble in Transfer Case - BW 4473-NP3 Unit Repair. Replace the front output shaft seal. Refer to Transfer Case Output Shaft Seal Replacement - Front .
Leaking at the ventTransfer case overfilled Inspect for the correct transfer case fluid level. Refer to Transfer Case Fluid Replacement . Inspect the transmission fluid level. Refer to Transmission Fluid Checking Procedure in Automatic Transmission 4L60-E. If the transmission fluid level is low, and the transfer case fluid level is too high, replace the transfer case input shaft seal. Refer to Transfer Case 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 vent if it is leaking at the case. Refer to Transfer Case Disassemble and Transfer Case Assemble in Transfer Case - BW 4473-NP3 Unit Repair.
Front case half to rear case half seam leakDisassemble, and seal the case halves again. Refer to Transfer Case Disassemble and Transfer Case Assemble in Transfer Case - BW 4473-NP3 Unit Repair.
Transfer case to adapter leakInspect for the following conditions: Loose mounting fasteners Gasket or sealant faulty The transfer case input shaft seal leaking Repair or replace the following components if found faulty: Replace the transfer case input shaft seal. Refer to Transfer Case 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 Repair or replace the loose fasteners. Refer to Adapter Replacement . Replace the transfer case adapter gasket. Refer to Adapter Replacement .
Case leakingInspect for a cracked case or case porosity. Replace the faulty case half. Refer to Transfer Case Disassemble and Transfer Case Assemble in Transfer Case - BW 4473-NP3 Unit Repair.

Transfer Case Leak Diagnosis

Transfer Case Viscous Coupling Test

Tools Required: J 45382 Transfer Case Tester. See Special Tools and Equipment .

IMPORTANTDo not operate the vehicle on a hoist to diagnose the driveline components. Operating the vehicle on a hoist can cause over-spinning of the planetary pinion gears. Testing the viscous coupling operation by removing a propeller shaft and driving the vehicle causes the viscous coupling to fail.

To determine if the viscous coupling is operating correctly, use the following test procedure. The test determines if the viscous coupling is faulty from a totally locked up failure, or if the viscous coupling fluid has leaked out from being severely humped.

  1. Operate the vehicle for 24 km (15 mi), or until normal operating temperatures are reached.
  2. Set the parking brakes for the rear wheels.
  3. Position the transmission in NEUTRAL.
  4. Raise the vehicle. Refer to «Lifting and Jacking the Vehicle»(/chevrolet/chevy-express-g3500/1996-2012/remont/hoistjack/#general-information__lifting-and-jacking-the-vehicle) in General Information.
  5. Remove the front propeller shaft. Refer to «Propeller Shaft Replacement - Front»(/chevrolet/chevy-express-g3500/1996-2012/remont/driveshaft-universal-joints/#propeller-shaft-and-universal-joints) in Propeller Shaft.
  6. Install the J 45382 into the transfer case front output shaft. See «Special Tools and Equipment»(/chevrolet/chevy-express-g3500/1996-2012/remont/transfer-case/#transfer-case-bw-4473-np3) .
  7. Using a torque wrench at 11 N.m (100 lb in) on the J 45382 , turn the front output shaft 90 degrees. See «Special Tools and Equipment»(/chevrolet/chevy-express-g3500/1996-2012/remont/transfer-case/#transfer-case-bw-4473-np3) .
  8. Note the length of time it takes to turn the front output shaft the 90 degrees. If the front output shaft turns slow, and takes at least 10 seconds, the viscous coupling is operating correctly. If the front output shaft will not turn, the viscous coupling or the planetary carrier assembly could be locked-up. If the front output shaft turns easily, and the 11 N.m (100 lb in) cannot be obtained, the viscous coupling is faulty.

Removal Procedure

IMPORTANTWhen performing the following service procedures, use only hand tools to remove and install the fill or drain plugs.
  1. Raise the vehicle. Refer to «Lifting and Jacking the Vehicle»(/chevrolet/chevy-express-g3500/1996-2012/remont/hoistjack/#general-information__lifting-and-jacking-the-vehicle) in General Information.
  2. Remove the fill plug from the transfer case.
  3. Remove the drain plug from the transfer case.

Installation Procedure

  1. Apply pipe sealant GM P/N 12346004 (Canadian P/N 10953480) to the threads on the drain plug.
  2. Install the drain plug in the transfer case. Tighten: Tighten the drain plug to 25 N.m (18 lb ft).
  3. Fill the transfer case to the bottom of the fill hole with the proper fluid.
  4. Apply pipe sealant GM P/N 12346004 (Canadian P/N 10953480) to the threads on the drain plug.
  5. Install the fill plug. Tighten: Tighten the fill plug to 25 N.m (18 lb ft).
  6. Disconnect the electrical connector from the speed sensor.
  7. Remove the speed sensor and the O-ring from the transfer case.
  8. Add 1.0 Liter (1.06 quarts) of DEXRON®VI fluid, P/N 88861003 (in Canada, P/N 88861004) through the threaded speed sensor opening.
  9. Install the speed sensor into the transfer case with the new O-ring seal. Tighten the fill plug to 17 N.m (13 lb ft).
  10. Connect the electrical connector to the speed sensor.
  11. Lower the vehicle. Refer to «Lifting and Jacking the Vehicle»(/chevrolet/chevy-express-g3500/1996-2012/remont/hoistjack/#general-information__lifting-and-jacking-the-vehicle) in General Information.
  1. Raise the vehicle. Refer to «Lifting and Jacking the Vehicle»(/chevrolet/chevy-express-g3500/1996-2012/remont/hoistjack/#general-information__lifting-and-jacking-the-vehicle) in General Information.
  2. Remove the electrical connector from the speed sensor.
  3. Remove the speed sensor and the O-ring from the transfer case.
  1. Install the new speed sensor into the transfer case with a new O-ring seal. Tighten: Tighten the right rear speed sensor to 17 N.m (13 lb ft).
  2. Install the electrical connector to the speed sensor.
  3. Lower the vehicle. Refer to «Lifting and Jacking the Vehicle»(/chevrolet/chevy-express-g3500/1996-2012/remont/hoistjack/#general-information__lifting-and-jacking-the-vehicle) in General Information.

Transfer Case Output Shaft Seal Replacement - Front

Tools Required

  1. J 8092 Universal Handle. See «Special Tools and Equipment»(/chevrolet/chevy-express-g3500/1996-2012/remont/transfer-case/#transfer-case-bw-4473-np3) .
  2. J 43484 Front Output Shaft Seal Installer. See «Special Tools and Equipment»(/chevrolet/chevy-express-g3500/1996-2012/remont/transfer-case/#transfer-case-bw-4473-np3) .
  1. Raise the vehicle. Refer to «Lifting and Jacking the Vehicle»(/chevrolet/chevy-express-g3500/1996-2012/remont/hoistjack/#general-information__lifting-and-jacking-the-vehicle) in General Information.
  2. Remove the front propeller shaft from the vehicle. Refer to «Propeller Shaft Replacement - Front»(/chevrolet/chevy-express-g3500/1996-2012/remont/driveshaft-universal-joints/#propeller-shaft-and-universal-joints) in Propeller Shaft.
  3. Insert a flat-tipped screw driver in the inner race.
  4. Pry the inner race forward.
  5. Insert a small pry bar in the inner race.
  6. Pry the inner part of the seal from the outer seal body.
  7. Remove the inner part of the seal.
  8. Insert a flat-tipped screw driver or small pry bar in the space between the outer race of the seal and the transfer case.
  9. Pry the outer race out of the transfer case.
  10. Remove the outer part of the seal.
  1. Using the J 43484 (2) and the J 8092 (1), install the transfer case output seal. See «Special Tools and Equipment»(/chevrolet/chevy-express-g3500/1996-2012/remont/transfer-case/#transfer-case-bw-4473-np3) .
  2. Install the front propeller shaft. Refer to «Propeller Shaft Replacement - Front»(/chevrolet/chevy-express-g3500/1996-2012/remont/driveshaft-universal-joints/#propeller-shaft-and-universal-joints) in Propeller Shaft.
  3. Check the transfer case fluid level. Refer to «Transfer Case Fluid Replacement»(/chevrolet/chevy-express-g3500/1996-2012/remont/transfer-case/#transfer-case-bw-4473-np3) .
  4. Lower the vehicle. Refer to «Lifting and Jacking the Vehicle»(/chevrolet/chevy-express-g3500/1996-2012/remont/hoistjack/#general-information__lifting-and-jacking-the-vehicle) in General Information.

Tools Required

J 45756 Rear Output Shaft Seal Installer. See Special Tools and Equipment .

  1. Raise and suitably support the vehicle. Refer to «Lifting and Jacking the Vehicle»(/chevrolet/chevy-express-g3500/1996-2012/remont/hoistjack/#general-information__lifting-and-jacking-the-vehicle) in General Information.
  2. Remove the rear propeller shaft. Refer to «Propeller Shaft Replacement - One Piece»(/chevrolet/chevy-express-g3500/1996-2012/remont/driveshaft-universal-joints/#propeller-shaft-and-universal-joints) in Propeller Shaft.
  3. Remove the rear output shaft seal by prying it out with a flat tipped screwdriver.
  1. Using J 45756 , install a new rear output shaft seal. See «Special Tools and Equipment»(/chevrolet/chevy-express-g3500/1996-2012/remont/transfer-case/#transfer-case-bw-4473-np3) .
  2. Install the rear propeller shaft. Refer to «Propeller Shaft Replacement - One Piece»(/chevrolet/chevy-express-g3500/1996-2012/remont/driveshaft-universal-joints/#propeller-shaft-and-universal-joints) in Propeller Shaft.
  3. Check the fluid level. Add fluid, if necessary.
  4. Lower the vehicle.
  1. Raise the vehicle. Refer to «Lifting and Jacking the Vehicle»(/chevrolet/chevy-express-g3500/1996-2012/remont/hoistjack/#general-information__lifting-and-jacking-the-vehicle) in General Information.
  2. Remove the transmission support member. Refer to «Transmission Support Replacement»(/chevrolet/chevy-express-g3500/1996-2012/remont/frames-subframes-crossmembers/#frame-and-underbody) .
  3. Drain the transfer case. Refer to «Transfer Case Fluid Replacement»(/chevrolet/chevy-express-g3500/1996-2012/remont/transfer-case/#transfer-case-bw-4473-np3) .
  4. Remove the rear propeller shaft from the transfer case. Refer to «Propeller Shaft Replacement - One Piece»(/chevrolet/chevy-express-g3500/1996-2012/remont/driveshaft-universal-joints/#propeller-shaft-and-universal-joints) in Propeller Shaft.
  5. Remove the front propeller shaft from the transfer case. Refer to «Propeller Shaft Replacement - Front»(/chevrolet/chevy-express-g3500/1996-2012/remont/driveshaft-universal-joints/#propeller-shaft-and-universal-joints) in Propeller Shaft.
  6. Remove the vent hose from the transfer case.
  7. Disconnect the electrical connector from the speed sensor.
  8. Unclip the fuel lines from the fuel line bracket.
  9. Install a suitable transmission jack to the transfer case.
  10. Remove the nuts from the transfer case to the adapter.
  11. Remove the transfer case from the transfer case adapter.
  12. Rotate the transfer case so that the transfer case is perpendicular to the torsion bar mounting bracket.
  13. Lower the transfer case.
  14. Remove the gasket from the transfer case.
  15. Remove the transfer case from the transmission jack.
  1. Install the transfer case on a suitable transmission jack.
  2. Install a new transfer case adapter gasket.
  3. Rotate the transfer case so that the transfer case is parallel to the torsion bar mounting bracket.
  4. Raise the transfer case into position.
  5. Rotate the transfer case so that the transfer case is aligned with the adapter.
  6. Install the transfer case on the adapter.
  7. Install the mounting nuts for the transfer case. Tighten: Tighten the mounting nuts to 50 N.m (37 lb ft).
  8. Install the transmission support member. Refer to «Transmission Support Replacement»(/chevrolet/chevy-express-g3500/1996-2012/remont/frames-subframes-crossmembers/#frame-and-underbody) .
  9. Remove the transmission jack.
  10. Install the electrical connector to the speed sensor.
  11. Install the vent hose to the vent tube.
  12. Install the fuel lines to the fuel line bracket.
  13. Install the front propeller shaft. Refer to «Propeller Shaft Replacement - Front»(/chevrolet/chevy-express-g3500/1996-2012/remont/driveshaft-universal-joints/#propeller-shaft-and-universal-joints) in Propeller Shaft.
  14. Install the rear propeller shaft. Refer to «Propeller Shaft Replacement - One Piece»(/chevrolet/chevy-express-g3500/1996-2012/remont/driveshaft-universal-joints/#propeller-shaft-and-universal-joints) in Propeller Shaft.
  15. Fill the transfer case with the proper transfer case fluid. Refer to «Transfer Case Fluid Replacement»(/chevrolet/chevy-express-g3500/1996-2012/remont/transfer-case/#transfer-case-bw-4473-np3) .
  16. Lower the vehicle. Refer to «Lifting and Jacking the Vehicle»(/chevrolet/chevy-express-g3500/1996-2012/remont/hoistjack/#general-information__lifting-and-jacking-the-vehicle) in General Information.
  1. Raise the vehicle. Refer to «Lifting and Jacking the Vehicle»(/chevrolet/chevy-express-g3500/1996-2012/remont/hoistjack/#general-information__lifting-and-jacking-the-vehicle) in General Information.
  2. Remove the transfer case from the vehicle. Refer to «Transfer Case Assembly Replacement»(/chevrolet/chevy-express-g3500/1996-2012/remont/transfer-case/#transfer-case-bw-4473-np3) .
  3. Remove the mounting bolts from the adapter to the transmission.
  4. Remove the adapter from the transmission.
  5. Remove the seal between the transfer case and the adapter.
  6. Remove the transfer case to the adapter gasket.
  1. Install the new seal on the adapter.
  2. Install the adapter to the transmission.
  3. Install the adapter mounting bolts to the transmission. Tighten: Tighten the mounting bolts to 50 N.m (37 lb ft).
  4. Install the new gasket to the adapter.
  5. Install the transfer case to the adapter. Refer to «Transfer Case Assembly Replacement»(/chevrolet/chevy-express-g3500/1996-2012/remont/transfer-case/#transfer-case-bw-4473-np3) .
  6. Install the transmission support member. Refer to «Transmission Support Replacement»(/chevrolet/chevy-express-g3500/1996-2012/remont/frames-subframes-crossmembers/#frame-and-underbody) .
  7. Remove the transmission jack from the transmission.
  8. Check the fluid level of the transfer case. Refer to «Transfer Case Fluid Replacement»(/chevrolet/chevy-express-g3500/1996-2012/remont/transfer-case/#transfer-case-bw-4473-np3) .
  9. Lower the vehicle. Refer to «Lifting and Jacking the Vehicle»(/chevrolet/chevy-express-g3500/1996-2012/remont/hoistjack/#general-information__lifting-and-jacking-the-vehicle) in General Information.

Transfer Case Input Shaft Seal Replacement

Tools Required

  1. J 45758 Seal Installer. See «Special Tools and Equipment»(/chevrolet/chevy-express-g3500/1996-2012/remont/transfer-case/#transfer-case-bw-4473-np3) .
  2. J 36825 Output Shaft Oil Seal Remover. See «Special Tools and Equipment»(/chevrolet/chevy-express-g3500/1996-2012/remont/transfer-case/#transfer-case-bw-4473-np3) .
  3. J 23907 Slide Hammer. See «Special Tools and Equipment»(/chevrolet/chevy-express-g3500/1996-2012/remont/transfer-case/#transfer-case-bw-4473-np3) .

Scheme 25

Scheme 25: Removal Procedure
Scheme 25: Removal Procedure
  1. Raise the vehicle. Refer to «Lifting and Jacking the Vehicle»(/chevrolet/chevy-express-g3500/1996-2012/remont/hoistjack/#general-information__lifting-and-jacking-the-vehicle) in General Information.
  2. Remove the transfer case from the adapter. Refer to «Transfer Case Assembly Replacement»(/chevrolet/chevy-express-g3500/1996-2012/remont/transfer-case/#transfer-case-bw-4473-np3) .
  3. Using the J 36825 (2) and J 23907 (1) remove the input shaft seal. See «Special Tools and Equipment»(/chevrolet/chevy-express-g3500/1996-2012/remont/transfer-case/#transfer-case-bw-4473-np3) . Poke a hole in the seal using a very small punch. Thread the tool J 36825 (2) into the hole. See «Special Tools and Equipment»(/chevrolet/chevy-express-g3500/1996-2012/remont/transfer-case/#transfer-case-bw-4473-np3) .
  1. Position the seal on the input shaft.
  2. Using the J 45758 , install the input shaft seal in the transfer case. See «Special Tools and Equipment»(/chevrolet/chevy-express-g3500/1996-2012/remont/transfer-case/#transfer-case-bw-4473-np3) .
  3. Install the transfer case to the adapter. Refer to «Transfer Case Assembly Replacement»(/chevrolet/chevy-express-g3500/1996-2012/remont/transfer-case/#transfer-case-bw-4473-np3) .
  4. Lower the vehicle. Refer to «Lifting and Jacking the Vehicle»(/chevrolet/chevy-express-g3500/1996-2012/remont/hoistjack/#general-information__lifting-and-jacking-the-vehicle) in General Information.

General Description

The Borg Warner (BW) model 4473 RPO NP3 transfer case is a one-speed, full time AWD, transfer case. The BW 4473 provides one operating mode, 4HI full-time AWD. The transfer case has a planetary differential gear set, which provides a 35 percent/65 percent torque split, front/rear, full time. Both axles are constantly being driven for maximum traction, and the best balance of vehicle handling characteristics under all operating conditions is provided.

The BW 4473 case halves are high-pressure die-cast aluminum. The transfer case requires DEXRON®III ATF Fluid GM P/N 12346143 (Canadian P/N 10952622), which is red in color.

Scheme 26

Scheme 26: General Description
Scheme 26: General Description

The power flows from the transmission to the transfer case input shaft (1). The input shaft (1) delivers the power to the planetary center differential (4), which splits the torque 35 percent through the differential pinion gears (8) to the front sun gear (7), through the sprocket drive (2), via the chain (10) to the front output shaft (9) and to the front propeller shaft. 65 percent of the torque is delivered to the rear output, which goes through the differential ring gear (6), which is connected to the rear output shaft (5), and to the rear propeller shaft.

The viscous coupling (3), torque biasing device, has a series of opposing discs which are attached to the front and rear output shafts. One set turns with the front axle and the one set turns with the rear axle. The viscous coupling has a sealed housing, which is filled with high viscosity silicone fluid. When there is a speed difference between front and rear axles, the inner and outer plates of the coupling turn relative to each other. The silicone fluid provides resistance to the speed difference, and torque is transferred to the axles to equalize the speed difference. The tuning of the coupling is such that binding is not felt in tight turns, on dry surfaces, while being high enough to bias torque quickly to the wheels that have traction in a vehicle slip event. If the speed difference between the axles is high, the viscous coupling can go into "hump" mode. This occurs when the heat generated by the high speed difference expands the viscous fluid in the coupling, which results in pressure between the plates, forcing them in to contact each other, similar to a clutch pack. In the "hump" mode, the coupling can bias torque 100 percent to one axle. To prevent damage to the viscous coupling, the following should be avoided in the vehicle

  1. Do not tow with only two wheels on the ground.
  2. Do not drive with one propeller shaft removed.
  3. Do not drive with a mini spare tire for any extended period of time.
  4. Do not operate the vehicle on a hoist to diagnose the driveline components.

Customers may have concern that the transfer case is not operating properly, because one set of tires spun for a brief period. It is normal for one set of tires to spin until the viscous coupling engages. Turning off the traction control switch, if equipped, enhances the function of the viscous coupling. The viscous coupling, as described above, engages by heat. Allowing one set of tires to spin or slip for a very brief period, generates heat in the viscous coupling. The engine speed should be kept at a constant speed during the brief spin of the tires. Feathering the engine speed, or hard acceleration, will not allow the viscous coupling to operate properly.

Scheme 27

Scheme 27: Power Flow - No Wheel Slip
Scheme 27: Power Flow - No Wheel Slip

During normal operation, 100 percent engine torque is delivered to the input shaft (1) from the transmission. The torque is split 65 percent to the rear output shaft (5), and 35 percent to the front output shaft (9), by the planetary differential (4). Because there is not a loss in traction, or slip in the front or rear wheels, the viscous coupling (3) is locked in place and there is no "shear" mode or "hump" mode involved.

Scheme 28

Scheme 28: Power Flow - Front Wheel Slip
Scheme 28: Power Flow - Front Wheel Slip

When traction is lost at the front wheels, the viscous coupling (3) works in conjunction with the planetary differential (4) to bias the torque more to the rear wheels. The rear torque goes higher than 65 percent, up to 100 percent torque to the rear output shaft (5). The torque at the front output shaft (9) is lowered from 35 percent, to as low as 0 percent torque.

Scheme 29

Scheme 29: Power Flow - Rear Wheel Slip
Scheme 29: Power Flow - Rear Wheel Slip

When traction is lost at the rear wheels, the torque is biased to the front wheels. The torque to the front output shaft (9) goes higher than 35 percent, up to 100 percent. The torque at the rear output shaft (5) is lowered from 65 percent, to as low as 0 percent torque.

Special Tools

Special Tools Illustration Tool Number/Description J 8092 Universal Driver J 23907 Slide Hammer J 36825 Output Shaft Oil Seal Remover J 43484 Front Output Shaft Seal Installer J 45382 Transfer Case Tester J 45756 Rear Output Shaft Seal Installer J 45758 Input Seal Installer

Scheme 30

Scheme 30: Special Tools
Scheme 30: Special Tools

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Scheme 31

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Scheme 32
Scheme 32

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Scheme 34

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