• If you currently own, previously owned or want to own an Avalanche, we welcome you to become a member today. Membership is FREE, register now!

RPO NP8 Transfer Case - Service

sperry

Silent Avalanche RIP
SM 2007
SM 2006
SM 2005
Full Member
Joined
Oct 22, 2003
Messages
13,160
Location
Seligman, AZ
Note: Content within this and other topics in this section are for CAFCNA Members only. It is NOT for commercial use in ANY form, by anyone. (Except GM)

Note:This document took almost 4? hours to prepare, debug and post BB code and uploading 67 exclusive images plus trimming text and code for fit. :C: I hope it will help someone in need!

-------------------------------------------------------------------------​

NP8 Transfer Case Disassemble / Reassemble

Tools Required

Available from: SPX Kent-Moore.

  ? J 3289-20 Holding Fixture
  ? J 8092 Universal Handle
  ? J 22873 Mainshaft Bushing Installer
  ? J 36370 Drive Sprocket Needle Bearing Installer
  ? J 36850 Transjel Lubricant
  ? J 37668-A Seal Installer
  ? J 42737 Sector Bearing Installer
  ? J 42738 Seal Installer
  ? J 43484 Seal Installer
  ? J 44295 Clutch Pack Shimming Kit
  ? J 45380 Transfer Case Rear Bushing Remover and Installer
  ? J 45383 Input Gear Pilot Bearing Installer
  ? J 45759 Assembly Fixture

      Notice: Refer to Fastener Notice.



  1. If removed, install the transfer case mounting studs to the height of 29.5 mm-30.5 mm (1.16-1.20 in).



  2. Attach the J 45759 to the front transfer case using the adapter studs. All of the assembly procedures can be performed with the case mounted to the J 45759 .
  3. Install the J 45759  (2) into the J 3289-20  (1) and secure with the pivot pin.



      Important:Use only new retaining rings.

  4. Install the input bearing. The cage side of the bearing faces to the case front.



  5. Install the input bearing retaining ring.



  6. Install the front output shaft ft. bearing. The cage side of the bearing faces to the ft. of the case.
  7. Install the front output shaft ft. bearing retaining ring.



  8. Using the J 8092  (1) and the J 36370  (2), install the ft. output shaft rear bearing.
        - The lettering on the bearing faces toward the tool.
        - Use the double shoulder side of the J 36370 to install the bearing recessed in the bore.



  9. Using the J 42737 , install the control actuator lever shaft bearing. The seal on the bearing faces outward.



  10. Using transfer case fluid, lubricate the control actuator lever shaft bearing.
  11. Install the control actuator lever shaft.



  12. Install the NEW retaining ring for the control actuator lever shaft. Ensure the retaining ring is fully seated.



  13. If it is a new shaft, or if the cup plug was removed, install the cup plug in the ft. output shaft using a suitable driver.



  14. Using the J 22873 and a hydraulic press, install a NEW tone wheel on the front output shaft.



  15. Install the ft. output shaft assembly. Use a soft-face hammer to tap the ft. output shaft into the bearing.



  16. Install the ft. output shaft retaining ring.



      Important: Depending on the version of the transfer case, it may have either a 4 pinion gear or 6 pinion gear planetary carrier assembly. The 4 pinion gear planetary carrier is used with transmission RPO M30 and the input gear splines are 27 teeth. The 6 pinion gear planetary carrier is used with transmission RPO MT1 and MN8 and the input gear splines are 32 teeth. The repair procedures are the same for both planetary carriers.

  17. Lubricate the thrust washer for the input shaft with J 36850 or equivalent.
  18. Install the input shaft thrust washer. Align the tabs on the thrust washer with the slots in the planetary carrier.



  19. Using the J 8092  (1) and the J 45383  (2), install the pilot bearing in the input shaft.



  20. Install the input shaft assembly.



  21. Lubricate the input shaft thrust washer with J 36850 or equivalent.
  22. Install the input shaft thrust washer.



  23. Lubricate the carrier lock ring with J 36850 or equivalent.
  24. Install the carrier lock ring. If there are letters on the lock ring, install with the lettering facing up.



  25. Install the ret. ring for the planetary gear shaft.



  26. Install the planetary gear carrier. Use a soft-face hammer to tap the input shaft into the bearing.



  27. Install the outer retaining ring for the input gear bearing.



  28. Install new shift fork pads, if removed.
  29. Install the range shift sleeve in the range fork.



  30. Align the range shift sleeve on the planetary carrier.
  31. Align the roller on the range fork in the control actuator lever slot.
  32. Install the range shift fork.



  33. Install the shift fork shaft.



  34. Install the clutch lever assembly.



      Important: When performing the following service procedure, ensure that the clutch lever pivot pins are tightened evenly. Ensure that the clutch lever moves freely after the pivot pins are tightened and engaging the lever.

  35. Install new O-ring seals on the clutch lever pivot pins.
  36. Lubricate the O-ring seals with xfer case fluid.
  37. Apply threadlock GM P/N 12345493 (Canadian P/N 1095348:cool:, or equivalent, to the clutch lever pivot pin threads.

      Notice: Refer to Fastener Notice.

  38. Install the clutch lever pivot pins with the aluminum washers and O-ring seals in the ft. case half.

      Tighten
      Tighten the clutch lever pivot pins to 61 N?m (45 lb ft).



      Important: Ensure that the shift detent plunger is seated correctly on the control actuator lever.

  39. Install the shift detent plunger.
  40. Install the shift detent spring.
  41. Lightly lubricate a NEW shift detent plunger O-ring seal with transfer case fluid.
  42. Install the O-ring seal on the shift detent spring bolt.
  43. Install the shift detent spring bolt in the front transfer case.

      Tighten
      Tighten the shift detent spring bolt to 17 N?m (13 lb ft).



      Important: The following service procedure is to be performed only if the rear output shaft is new.
  44. Install the rear output shaft oil restrictor flush with the end of the shaft.



      Important: In order to position the bearing at the proper depth, ensure that the double shoulder of the J 36370 is against the bearing.

  45. Using the J 8092  (1) and the J 36370  (2), install the clutch housing bearing.



  46. Clamp the rear output shaft in a soft-jaw vise with the front end facing up.
  47. Install the clutch housing on the rear output shaft.



  48. Install the clutch hub.



  49. Install the clutch hub oil restrictor plate. The fingers of the oil restrictor plate face up.



  50. Install the clutch pressure plate inner in the clutch housing, with the notch in the plate facing down.



  51. Install a friction clutch pressure plate.
  52. Install a steel clutch pressure plate.
  53. Continue to install the friction and the steel clutch plates, alternating until 10 friction plates and 9 steel plates are installed.



  54. Install the clutch hub ret. ring.



      Important: A clutch plate shim package is necessary in order to have the proper shims available for setting the correct clutch pack preload. Improper preload can cause driveability concerns & failure of the transfer case.


  55. Securely install the base plate (3) of the J 44295 in a vise with the machined surface of the locating tabs facing up.
  56. Install the assembled rear output shaft with the clutch housing, the inner clutch plates, and the outer clutch plates on the base plate (3) of the J 44295 .
  57. Install the weight (1) of the J 44295 on top of the assembled clutch plates.
  58. Place the gage block (2) of the J 44295 on 1 of the locating tabs of the base plate (3) of the J 44295 .
  59. Using a feeler gage, measure between the gage block (2) and the weight (1) of the J 44295 .
  60. Measure with the gage block (2) and the feeler gage on the remaining 2 locating tabs of the base plate (3).

      Important: The specification is the average clearance remaining between the weight (1) and the gage block (2).

  61. The average of the 3 measurements is the required shim thickness.

      Important: Measure the clutch shims in the center area of the shim. The shims may have a burr or ridge around the inner or outer edge causing an incorrect measurement. The available shims may not combine to the desired measurement.

  62. Select from the clutch plate shim package the correct shim or shims plus or minus 0.10 mm (0.004 in). You may use a combination of 2 shims to obtain the correct thickness.

      The shims in the clutch plate shim package are the following thickness:

        - 0.30 mm (0.12 in)
        - 0.56 mm (0.022 in)
        - 0.81 mm (0.032 in)
        - 1.04 mm (0.041 in)
        - 1.30 mm (0.051 in)
        - 1.55 mm (0.061 in)
        - 1.80 mm (0.071 in)
        - 2.08 mm (0.081 in)

  63. Remove the weight (1) of the J 44295 .

    Important: After obtaining the desired thickness of shims, do not remove the clutch plates from the clutch housing. If you remove, and then install the clutch plates again, it could change the measurement.

  64. Install the shim or shims.



  65. Using a suitable press plate & a hydraulic press, press the clutch bearing inner support in the clutch apply plate bearing. Ensure the bearing inner bearing race is supported.



  66. Install the clutch apply plate bearing & inner support in the clutch apply plate.



  67. Install the clutch pressure plate spring.
  68. Align the tabs on the clutch pressure plate with the grooves in the clutch hub & install the clutch pressure plate assembly.



  69. Install the clutch apply plate retaining ring. Push down on the apply plate to access the retaining ring groove.



  70. Align the tab on the clutch inner support bearing hub with the clutch lever.
  71. Align the rear output shaft teeth to the planetary carrier & range sleeve teeth.
  72. Install the rear output shaft assembly.



      Important: Ensure to align the marks of the drive chain and sprockets if using the chain and sprockets again.

  73. Install the drive chain and sprockets. The blue chain links must face up or toward the rear of the vehicle.



  74. Install the drive sprocket ret. ring.



Note: Do to posting size limits, the code used to expand the following images was deleted.

  75. Install the driven sprocket ret. ring.

normal_892466.gif


      Important: The rear output shaft may be an original design (2) or the replacement design (1). The original design rear output shaft (2) uses an oil pump wave washer above the oil pump & a retaining ring under the oil pump. The original design rear output shaft (2) is identified by the splines in the area by the oil gallery hole. The replacement design rear output shaft has a smooth area by the oil gallery hole. Ensure to follow the steps for the correct rear output shaft.

  76. Inspect the rear output shaft to identify as an original design (2) or the repl. design (1).

normal_163898.gif


  77. If an original design rear output shaft, install the oil pump retaining ring onto the rear output shaft. Ensure the retaining ring is not positioned over the oil hole on the rear output shaft.

normal_163888.gif


  78. Install a new oil pump suction pipe O-ring in the oil pump.

normal_886580.gif


  79. Install the oil pump assembly.
  80. If an original design rear output shaft, install the oil pump wave washer.

normal_163872.gif


  81. Install the oil pump screen.
  82. Install the connector on the oil pump screen.
  83. Install the oil pump suction pipe to the oil pump.
  84. Connect the oil pump suction pipe to the connector.

normal_163856.gif
[/url]

  85. Install the transfer case magnet.

normal_701592.gif


  86. Install the rear output shaft speed reluctor wheel.

normal_701589.gif


      Important: Install the rear output shaft bearing with the groove for the retaining ring facing up.

  87. Install the rear output shaft bearing.

normal_701586.gif


  88. Install the rear output shaft bearing retaining ring. Push down on the rear output shaft bearing to compress the oil pump wave spring.
  89. Align the outside retaining ring for the rear output shaft bearing so that it is easily accessed through the opening in the rear case half.

normal_724251.gif


    Important: A new oil pump wear sleeve may have a star shaped hole or a spring clip hole.

  90. If necessary, install the oil pump wear sleeve.
  91. Lightly stake the oil pump wear sleeve pin to hold the sleeve in place, if star shaped hole style.

normal_163815.gif
[/url]

    Important: Ensure the locating pins are installed in the front case half.

  92. Install the locating pins in the front case, if necessary.

normal_698077.gif


      Notice: Apply the proper amount of sealant to the flange when assembling the transfer case. Excessive amounts of sealant can plug the oil pump screen, resulting in internal component failure.

      Important: Ensure both sealing surfaces of the ft. & rear case halves are free of dirt, oil, & cleaning solvent.

  93. Apply a 3 mm (1/8 in) bead of RTV sealant GM P/N 12345739 (Canadian P/N 10953541) or equivalent to the mating surfaces of the ft. case half.

normal_163737.gif


  94. Lower the rear case half in to place.

normal_649760.gif


  95. Using a pair of snap ring pliers, open the ret. ring for the rear output shaft bearing.
  96. Insert a rubber coated screwdriver into 1 of the speed sensor holes & lift up on the speed reluctor wheel, then seat the ret. ring.

normal_163733.gif


      Notice: This component is made of magnesium. Proper assembly is required to prevent damage. Ensure the magnesium transfer case housings are properly insulated from all external steel components, or galvanic corrosion will occur. New nylon coated case bolts and aluminum washers must be used. Use only aluminum fill and drain plugs. Use only aluminum brackets under the case bolts. Ensure new seals are installed that have a rubber insulated outside diameter and have no tears or cuts. Extensive damage will occur if there is galvanic corrosion between the magnesium and steel components.

  97. Install the new case bolts, washers, & brackets.

      Tighten
      Tighten the case bolts to 37 N?m (27 lb ft).

normal_163722.gif


  98. Install the access hole plug.

normal_163714.gif


  99. Install new O-ring seals on the vehicle speed sensors.
100. Lubricate the veh. speed sensor O-ring seals with xfer case fluid.
101. Install the rear veh. speed sensors.

      Tighten
      Tighten the speed senor to 15 N?m (11 lb ft).

normal_662047.gif

   
102. Install the ft. vehicle speed sensor.

      Tighten
      Tighten the speed senor to 15 N?m (11 lb ft).

normal_804163.gif


103. Install the act. insulator to the transfer case.
104. Install the enc. motor to the transfer case. Rotate the control actuator lever shaft to align to the enc. motor.
105. Install the mounting bolts for the encoder motor.

      Tighten
      Tighten the encoder motor mounting bolts, in the sequence shown, to 20 N?m (15 lb ft).

normal_801307%7E0.gif


106. Using the J 45380 , install a new rear output shaft bushing.
        1. Install the bushing on the finger section of the J 45380 .
        2. Install the finger section to the main body of the J 45380 .
        3. Position the bushing and tool to the case.
        4. Using a hammer and the J 45380 , install the bushing.

normal_687288%7E0.gif


107. Align the rear output shaft seal to the rear case, with the square tab up and the drain hole down.
108. Using the J 37668-A , install the rear output shaft seal.

normal_678236.gif


109. Using the J 43484  (2) and the J 8092  (1), install the front output shaft seal.

normal_678288.gif


110. Using the J 42738 , install the input shaft seal.

111. The transfer case is ready to reinstall.
 
DTC C0327

Circuit Description

The transfer case encoder is an analog sensor that returns a signal that represents the physical position of the transfer case sector shaft. This signal represents the mode or range position that the transfer case is currently in. This sensor is made up of the following 3 circuits:

    * A 5 volt reference circuit
    * An encoder signal circuit
    * An encoder low reference circuit

This DTC detects an out of range reading from the encoder signal, a short to voltage on the 5 volt reference circuit.

Conditions for Setting the DTC

The transfer case shift control module has a predefined range, 0.5-4.5 volts, in which the encoder feed back should stay within. The DTC sets if the encoder signal feed back falls out of this range.

Action Taken When the DTC Sets

    * All motor activity stops and the transfer case lock engages.
    * The SERVICE 4WD indicator remains illuminated for the remainder of the current ignition cycle.

Conditions for Clearing the DTC

    * The transfer case shift control module will clear the DTC if the condition for setting the DTC is not currently present.
    * A history DTC will clear after 100 consecutive ignition cycles without a fault present.
    * History DTCs can be cleared using a scan tool.

Test Description

The numbers below refer to the step numbers on the diagnostic table.

  2.      This step checks for a voltage reading on the scan tool.
  3.      This step tests the encoder circuit for a current malfunction.
  4.      This step tests for an internal encoder malfunction which is present only in certain areas of the encoder sensor.
  5.      This step tests for proper reference voltage at the encoder.
  6.      This step tests the 5 volt regulator encoder circuit for a short to voltage, short to ground, an open or high resistance.
  7.      After determining if the reference voltage measured in Step 4 is correct, Step 6 reviews the reading originally measured in Step 3 to see if it is higher or lower than what is expected. This step helps determine whether the encoder signal circuit is being pulled high or low.
  8.      This step tests the encoder signal circuit and the encoder low reference circuit for a short to voltage.
  9.      This step helps determine a faulty encoder.
  10.    This step tests the encoder signal circuit and the encoder low reference circuit for an open or a short to ground.

 

Attachments

  • 856251_DTC-C0327-Chart.gif
    856251_DTC-C0327-Chart.gif
    37.4 KB · Views: 623
GM Doc # 856265​

Transfer Case Shift Control Switch Indicator Always On - Two or More

Circuit Description

The indicator lamps circuit consist of the following 5 individual lamps contained inside the mode/range switch assembly:

    * 4HI
    * AUTO 4WD
    * 2HI
    * 4LO
    * Neutral

The following lamps are contained inside their respective range button:

    * 4HI
    * AUTO 4WD
    * 2HI
    * 4LO
    * Neutral

When the ignition in ON, the transfer case shift control module illuminates the indicator that corresponds to the current automatic temperature control (ATC) gear position by providing a ground through a current limiting driver.

The transfer case shift control module flashes each indicator lamp after a shift has been requested, and continues to flash until the transfer case shift control module can complete the shift.

A solid state circuit located inside the switch supplies ignition voltage to the lamps. The solid state circuit also receives voltage when the headlamp switch is in the parklamp or headlamp position. When the solid state circuit receives voltage from the headlamp switch, the switch reduces the voltage supplied to the indicator lamps, dimming the lamps when the headlamps are ON.

Test Description

The numbers below refer to the step numbers on the diagnostic table.

  2.      This step tests the transfer case electrical control of the lamp circuits.
  3.      This step helps determine if there is a short to ground in the suspect lamp circuits.
  4.      This step tests the suspect lamp circuits for a short to ground.
  5.      This step repairs a short to ground in the suspect lamp circuit.
 

Attachments

  • 856265-4WD-Two_or_More_Lights-Chart.gif
    856265-4WD-Two_or_More_Lights-Chart.gif
    20.3 KB · Views: 607
Here is a simple access to isolate a possible bad ground condition; sometimes the "Service 4WD" message is shared with ABS warnings.

Try cleaning the lugs and the frame paint from the frame under them. And of course, tighten the hardware a bit better than the assembler did!

Use a 13mm wrench or socket, a drill-powered wire brush on the frame and steel wool on the lugs, just enough to clean off the contaminants only (careful not to remove the "plating" or "tinning" from the terminals - replace them if they are too badly damaged.

(Click on the image to expand the view and detail.)


(1)  Frame
(2)  Electronic Brake Control Module (EBCM) Ground (GNO)
(3)  Manual Selectable Ride Ground (G302)
(4)  Automatic Transfer Case/ABS Ground (G110)

This part of the frame is under the driver's feet.
 
Back
Top