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SERIES 50 CAMSHAFT DRIVE GEAR

The camshaft drive gear, located at the front of the engine, under the gear case cover, is driven by the crankshaft through a series of intermediate gears. See Figure 24300 . ‪

1. Camshaft Idler Gear ‪

4. Bull Gear ‪

2. Adjustable Idler Gear ‪

5. Crankshaft Timing Gear ‪

3. Camshaft Drive Gear ‪

Engine Gear Train and Timing Marks

The gear train for the crankshaft drive consists of a crankshaft timing gear, mounted to the end of the crankshaft, meshing with a bull gear. To the rear of the bull gear is the camshaft idler gear, which is mounted on the same hub and rotates at the same speed as the bull gear. The camshaft idler gear meshes with an adjustable idler gear, which is mounted on a separate hub. The adjustable idler gear in turn meshes with the camshaft drive gear, which is mounted on the camshaft drive gear hub. The gears are designed so that the camshaft is driven at half crankshaft speed. ‪

Since the camshaft must be timed exactly to the crankshaft, a series of timing marks are stamped or etched on the gear faces of these gears so that they may be installed in correct relationship to each other. Refer to Section . ‪

The camshaft drive gear is keyed and pressed onto a hub located in the thrust plate assembly at the end of the camshaft. The camshaft drive gear and hub are retained to the end of the camshaft by the camshaft drive gear retaining bolt which goes through the camshaft drive gear and the hub, and is threaded into the end of the camshaft. See Figure 34803 . ‪

1. Bolt, Thrust Plate Retaining (2) or (3) ‪

6. Gear Case ‪

2. Bolt, Camshaft Hub Retaining ‪

7. Seal, Thrust Plate ‪

3. Drive Gear. Camshaft ‪

8. Camshaft ‪

4. Thrust Plate, Camshaft ‪

9. Key ‪

5. O-ring ‪

10. Hub ‪

Camshaft Drive Gear and Related Parts

The camshaft is indexed to the hub by a dowel. The camshaft drive gear hub rides in a camshaft thrust plate, which is retained by three (current) or two (former) bolts. One of these bolts screws into the cylinder head, while the other bolt screws into the No. one camshaft bearing cap. ‪

The camshaft thrust plate is sealed to the gear case by an O-ring which fits into a groove machined in the outer diameter of the thrust plate. A diamond shaped rubber seal that fits into a groove machined in the rear camshaft thrust plate face, seals the camshaft thrust plate to the cylinder head and No. one camshaft cap. The dimple in the thrust plate must be installed at the 12 o'clock position to allow alignment of the thrust plate bolt holes with those in the cylinder head and No. 1 camshaft cap. See Figure 34802 . ‪

Camshaft Thrust Plate and Dowel Pin Location

The camshaft thrust plate can be moved horizontally in the gear case, to allow camshaft and cylinder head removal without damaging the thrust plate seal or removing the gear case cover. The camshaft drive gear will stay in mesh with its mating gear, and may be returned to its original position without retiming the gears. ‪

Repair or Replacement of Camshaft Drive Gear

To determine if repair or replacement of the camshaft drive gear is necessary, preform the following procedure. See Figure 24150 . ‪

Flowchart for Repair or Replacement of Camshaft Drive Gear

Removal of Camshaft Drive Gear

Remove the camshaft drive gear as follows: ‪

  1. Remove the engine rocker cover. Refer to Section .
  2. Remove the camshaft drive gear access cover, fan bracket and camshaft retaining bolt. Refer to Section .

    NOTICE:

    Use care when removing the camshaft thrust plate retaining bolts to prevent their accidental dropping into the gear case and causing engine damage. ‪

  3. Working through the access holes in the camshaft drive gear, remove the three (current) or two (former) bolts that retain the camshaft thrust plate to the cylinder head and No. 1 camshaft bearing cap. See Figure 34801 .

    1. Camshaft Thrust Plate Mounting Bolt Locations ‪

    Camshaft Thrust Plate Retaining Bolts

  4. Using the Camshaft Gear Pilot Tool, J 35906 , pull the cam gear thrust plate assembly forward as far as possible to separate the assembly from the camshaft.
  5. Remove the gear case cover. Refer to Section .
  6. Using a fiber mallet or plastic hammer, tap the rear face of the camshaft thrust plate forward until it is free of the gear case. See Figure 20262 .

    Removing Camshaft Thrust Plate Assembly

  7. Remove the camshaft thrust plate, hub, and camshaft drive gear as an assembly. See Figure 20263 .

    Camshaft Thrust Plate Assembly

  8. Support the camshaft drive gear, with thrust plate facing down, on blocks.
  9. Press the hub out of the camshaft drive gear until the hub separates from the camshaft thrust plate. See Figure 20264 .

    Camshaft Hub Removal

  10. Remove the O-ring and seal from grooves in the camshaft thrust plate. Discard O-ring and seal.
Inspection of Camshaft Drive Gear

Inspect camshaft drive gear as follows: ‪

  1. Clean all parts with fuel oil.

    EYE INJURY

    To avoid injury from flying debris when using compressed air, wear adequate eye protection (face shield or safety goggles) and do not exceed 40 psi (276 kPa) air pressure.

  2. Dry them with compressed air.
  3. Examine the camshaft drive gear teeth for scoring, pitting, excessive wear and cracking, peening of the Woodruff key slot.
  4. If camshaft drive gear is damaged, replace drive gear.
  5. Inspect the camshaft drive gear hub for scoring, pitting, galling or cracking, peening of the Woodruff key slot.
  6. If damaged, replace drive gear hub.

Installation of Camshaft Drive Gear

Install the camshaft drive gear, hub and thrust plate as follows: ‪

  1. Coat the contact surfaces of the hub and camshaft thrust plate with clean engine oil. See Figure 20247 .

    1. Woodruff Key ‪

    5. Groove, Seal ‪

    2. Hub, Camshaft Drive Gear ‪

    6. Dowel Hole, Camshaft ‪

    3. Drive Gear, Camshaft ‪

    7. Thrust Plate, Camshaft ‪

    4. Groove, O-ring ‪

    Cross Section of Camshaft Drive and Related Parts

  2. Install the hub to the camshaft thrust plate.
  3. Install the key into the keyway on the hub.
  4. Apply a thin film of Lubriplate to the bore of the camshaft gear.
  5. Support the hub from the engine side.

    NOTICE:

    A minimum force of 20 kN (4500 lb) must be obtained when pressing the gear on the hub which can distort camshaft gear if applied off center. Only apply force to the inner hub of the gear when pressing. ‪

  6. Align the keyway in the camshaft drive gear with the key in the hub and press the gear, timing markup, onto the hub until it is firmly seated against the shoulder.
Test of Camshaft Drive Gear Assembly Run-out

Measure the camshaft drive gear assembly run-out as follows: ‪

  1. While supporting the camshaft thrust plate on blocks, position the camshaft drive gear assembly with the engine side facing down.
  2. Assemble a dial indicator and magnetic base with the indicator stem rests on the face of the camshaft drive gear, just inboard of the drive gear teeth. Zero the dial indicator.
  3. Rotate the drive gear two full rotations while reading the total indicated run-out .

    Note: The total amount the dial indicator needle moves to the left and right of zero, added together, gives the total indicated run-out Total Indicator Reading (TIR).

    1. Maximum allowable TIR is 0.114 mm (0.0045 in.).
    2. If TIR exceeds limit, replace parts.

Installation of Camshaft Drive Gear

Continue installing camshaft drive gear assembly as follows: ‪

NOTICE:

Failure to install seals properly, failure to install new, dry (no lubrication) bolts where required, or failure to tighten bolts to the required torque using an accurately calibrated hand torque wrench may result in bolt loosening and loss of clamping load, which may cause severe engine damage. ‪

NOTICE:

Do not use RTV or any other type of sealant on the thrust plate perimeter seal. Application of sealant will prevent proper seal crush (flow), which may result in seal leakage. ‪

  1. Coat the camshaft thrust plate O-ring with clean engine oil.
  2. Install it into its groove in the camshaft thrust plate.
  3. Install diamond seal into its groove on the engine side of the thrust plate.

    The former two-bolt thrust plate oil seal design was redesigned to provide superior oil sealing characteristics. See Figure 35309 for design configuration. The current thrust plate oil seal uses a three bolt design, as of serial number 4R21236. ‪

    Camshaft Thrust Plate Oil Seal

  4. Be sure the O-ring sealing surface of the gear case is clean and free of burrs.
  5. Install the hub and camshaft thrust plate to the opening in the gear case. The depression in the rear face of the camshaft thrust plate must be positioned at 12 o'clock, see Figure 34802 , to align the retaining bolts in the thrust plate with those in the head and No. 1 cam cap.
  6. Using a fiber mallet or plastic hammer, tap the camshaft drive gear at 90 intervals toward the engine, until the thrust plate bolts can be started in the cylinder head and No. 1 camshaft cap.

    NOTICE:

    Ensure camshaft dowel hole in camshaft drive hub is aligned with camshaft dowel prior to tightening thrust plate bolts. A misaligned hub can cause damage to the camshaft and thrust plate components ‪

    NOTICE:

    Use care when installing the camshaft thrust plate retain bolts to prevent accidentally dropping them into the gear case and causing damage to gear train. ‪

  7. Using a 13 mm socket and ratchet, tighten the thrust plate bolts alternately and evenly to draw the thrust plate straight into the gear case. Torque the bolts to 30-38 Nm (22-28 lbft).
  8. Install gear case cover. Refer to Section .

    NOTICE:

    Always hold the camshaft drive gear stationary using camshaft drive gear retaining tool, J 35652-A part of J 35652 , to prevent component damage, while loosening or tightening the camshaft drive gear-to-camshaft bolt. ‪

  9. Once the gear case cover has been installed and secured, install the camshaft drive gear retaining tool, J 35652-A part of J 35652 .

    Note: Before installing the fan support bracket and camshaft drive gear access cover, it will be necessary to install and tighten the camshaft drive gear retaining bolt, and to measure and adjust the adjustable gear-to-camshaft drive gear lash.

  10. Install and torque the camshaft drive gear retaining bolt to 425 Nm (310 lbft).
  11. Check the gear train timing and adjustable idler gear-to-camshaft drive gear lash. Refer to Section .
  12. Install the camshaft drive gear access cover and fan bracket. Refer to Section .
  13. Install any components that were removed for access to the gear case cover.
  14. Check the lubricating oil. Refer to Section .
  15. Check the coolant level. Refer to Section .