Section 1.32
Bull Gear and Camshaft Idler Gear for the Compact Gear Train

The bull gear and camshaft idler gear assembly is centrally located beneath the gear case cover. The larger bull gear is directly driven by the crankshaft timing gear. The bull gear directly drives all of the gear-driven engine accessories (except the oil pump), meshing with drive gears for the fuel pump drive, air compressor drive and power steering pump (if so equipped), water pump and accessory and alternator drive.‪

Figure 1. Series 60 Compact Gear Train Assembly

The smaller camshaft idler gear is located behind the bull gear on the same carrier, and turns at the same speed as the bull gear. The camshaft idler gear drives an adjustable idler gear, mounted on a separate hub in the gear case. The adjustable idler gear drives the camshaft drive gear. The gear ratio of each gear in relationship to the crankshaft timing gear is shown directly below the gear title. See Figure "Series 60 Compact Gear Train Assembly" .‪

The bull gear and camshaft idler gear are installed on a spindle, the spindle is bolted to the engine block. ‪

The camshaft must be in time with the crankshaft timing gear. Timing marks have been stamped or etched on the face of the bull gear and crankshaft timing gear to facilitate correct gear train timing. See Figure "Compact Gear Train and Engine Timing Marks" .‪

Figure 2. Compact Gear Train and Engine Timing Marks

The backlash between the various mating gears in the gear train should be 0.051-0.229 mm (0.002 -0.009 in.), and should not exceed 0.305 mm (0.012 in.) backlash between worn gears.‪

Note: All gear lash measurements should be taken with engine in an upright position.

Section 1.32.1
Repair or Replacement of Bull Gear and Camshaft Idler Gear Assembly

To determine if repair or replacement of the bull gear and camshaft idler gear assembly is necessary, perform the following procedure. See Figure "Flowchart for Repair or Replacement of Bull Gear and Camshaft Idler Gear Assembly" .‪

Figure 3. Flowchart for Repair or Replacement of Bull Gear and Camshaft Idler Gear Assembly

Section 1.32.2
Removal of Bull Gear and Camshaft Idler Gear Assembly

To determine if repair or replacement of the bull gear and camshaft idler gear assembly is necessary, perform the following procedure.‪

1. Remove the engine gear case cover. Refer to "1.11.2 Removal of Gear Case Cover" .
2. Install J–35994 to the oil seal contact area of the crankshaft. See Figure "J–35994 Crankshaft Protector" .
   

   Figure 4. J–35994 Crankshaft Protector

   NOTICE:
   Use care when removing the bull gear and camshaft idler gear assembly from the engine so that it does not come in contact with the oil seal contact surface of the crankshaft. If this sealing surface is scratched, an oil leak may result.‪

3. Grasp the bull gear and pull the assembly straight out and off the spindle.

Section 1.32.2.1
Inspection of Bull Gear and Camshaft Idler Gear Assembly

Inspect the bull gear and camshaft idler gear assembly as follows:‪

1. Clean the bull gear and idler gear assembly in clean 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 276 kPa (40 psi) air pressure.‪

2. Dry the bull gear and idler gear assembly with compressed air.
3. Visually examine the gear teeth on both the bull gear and idler gear for evidence of scoring, cracking, pitting, and wear.
   1. If either gear is damaged, replace the bull gear and idler gear assembly.
   2. If either gear is not damaged, reuse the bull gear and idler gear assembly.
4. Visually examine the inner diameter of both gears, where they are pressed on the carrier for evidence of gear movement.
   1. If there is any evidence of gear movement, replace the bull gear and idler gear assembly.
   2. If damage is not found, reuse the bull gear and idler gear assembly.
5. Place the bull gear and idler gear assembly on a bench. Inspect the bushing for signs of distress or overheating.
   1. If there is any bushing distress, replace the bull gear and idler gear assembly.
   2. If damage is not found, reuse the bull gear and idler gear assembly.

Section 1.32.3
Installation of Bull Gear and Camshaft Idler Gear Assembly

Install the bull gear and camshaft idler gear assembly as follows:‪

1. Rotate crankshaft to TDC.
2. Install J–35994 to the oil seal contact area of the crankshaft. See Figure "J–35994 Crankshaft Protector" .

   Note: The crankshaft seal surface will be protected using J–35994 , when installing the bull gear and camshaft idler gear assembly to the cylinder block.

3. If removed install adjustable idler gear.Refer to "1.31 Adjustable Idler Gear Compact Gear Train" .

   NOTICE: ‪

   The bull gear is not attached and will slide off if engine is rotated.‪

4. Coat the contact areas of the bull gear and camshaft idler gear assembly with clean engine oil.
5. Align timing marks on bull gear and crankshaft timing gear. See Figure "Compact Gear Train and Engine Timing Marks" .
   

   1. Crankshaft Timing Gear‪	3. Timing Marks‪
   2. Bull Gear‪

   Figure 5. Compact Gear Train and Engine Timing Marks

6. Install bull gear onto spindle and install a new O-ring into spindle. See Figure "Bull Gear, Spindle and O-ring Location" .
   

   1. O-ring‪	3. Spindle‪
   2. Bull Gear‪

   Figure 6. Bull Gear, Spindle and O-ring Location

7. Install camshaft gear assembly. Refer to "1.26 Camshaft Gear Assembly Series 60 Exhaust Gas Recirculation (EGR) Model" .
8. Check the timing marks on the bull gear and crankshaft timing gear to ensure gear train is properly timed. See Figure "Compact Gear Train and Engine Timing Marks" .
9. Check the lash for all of the gears that mate with the bull gear and camshaft idler gear.Refer to "1.25 Compact Gear Train and Engine Timing" .
10. Install the gear case cover. Refer to "1.11.3 Installation of Gear Case Cover EGR Model" .
11. Check bull gear to accessory drive gear lash. Refer to "1.25.2.1 Check Engine Timing" .
12. Refer to "12 Operation and Verification" for verification of proper bull gear and camshaft idler gear assembly installation.