Series 60 – Section 1.31 Adjustable Idler Gear Compact Gear Train

Section 1.31
Adjustable Idler Gear Compact Gear Train

The adjustable idler gear is a straight-cut gear, mounted on a bushing pressed into the center of the gear, which in turn is supported on a stationary hub. The hub is secured to the gear case by a retaining plate, three bolt studs, and locknuts. One stud is pressed into the gear case from the rear, and the flanged locknuts are installed after the gear, hub and hub retaining plate are installed. See Figure "Adjustable Idler Gear and Related Parts" .‪

1. Nut‪	5. Gear Case‪
2. Retaining Plate, Adjustable Idler Gear Hub‪	6. Stud Bolts‪
3. Idler Gear‪
4.Idler Hub‪

Figure 1. Adjustable Idler Gear and Related Parts

The adjustable idler gear bushing has a series of machined grooves in the contact surface, for oil retention. The bushing is not serviced separately. If the bushing becomes worn or damaged, the gear and bushing must be replaced as an assembly.‪

There are three bolt holes in the idler hub, and a hub locating dowel which is drilled to supply oil to the bushing from a drilling in the block.‪

All holes are oversize, to allow the idler gear and idler hub assembly to be moved in relationship to the camshaft drive gear. This allows the adjustable idler hub to pivot on the locating dowel, so the adjustable idler gear to camshaft drive gear lash can be adjusted without changing the clearance between the adjustable idler gear and camshaft idler gear. The adjustable idler gear retaining plate has a flat on the bottom to clear the bull gear for removal and installation‪

Section 1.31.1
Repair or Replacement of Adjustable Idler Gear Assembly

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

Figure 2. Flowchart for Repair or Replacement of Adjustable Idler Gear Assembly

Section 1.31.2
Removal of Adjustable Idler Gear Assembly

Remove the adjustable as follows:‪

1. Drain the cooling system. Refer to "14.6.4 Cooling System" .
2. Drain the engine lubricating oil. Refer to "14.6.1 Lubricating Oil" .
3. Remove the oil pan. Refer to "3.11.2 Removal of Oil Pan" .
4. Remove the camshaft gear assembly.Refer to "1.26.2 Removal of Camshaft Gear Assembly" .
5. Remove the gear case cover. Refer to "1.11.2 Removal of Gear Case Cover" .

   NOTICE:
   Always use crankshaft protector (J–35994) to guard against damage to the oil seal area of the crankshaft. When removing the bull gear or camshaft idler gear and hub assembly, do not come in contact with the oil seal contact surface of the crankshaft. If sealing surface is scratched, an oil leak may result.‪

6. Install J–35994 to the oil seal contact area of the crankshaft. See Figure "J–35994 Crankshaft Protector" .
   

   Figure 3. J–35994 Crankshaft Protector

7. Remove bull gear and camshaft idler gear.Refer to "1.32.2 Removal of Bull Gear and Camshaft Idler Gear Assembly" .
8. Remove three adjustable idler gear nuts from stud and stud bolts. Discard nuts.
9. Remove the adjustable idler gear hub retaining plate.
10. Remove the adjustable idler gear and idler hub.

Section 1.31.2.1
Inspection of Adjustable Idler Gear Assembly

Inspect the adjustable idler gear as follows‪

1. Wash the adjustable idler gear, idler hub, and retaining plate thoroughly 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 with compressed air.
3. Examine the gear teeth for evidence of scoring, pitting and wear.

   Note: If gear teeth are damaged, also inspect the other gears in the gear train.

   1. If severely damaged or worn, replace the gear.
   2. If no damage is found, reuse the gear.
4. Inspect the contact surface of the idler hub for scoring or evidence of overheating (blue discoloration).
   1. If idler hub has blue discoloration, replace the idler hub.
   2. If idler hub has no blue discoloration, reuse the idler hub.
   3. If slight irregularities are present, use a fine stone or emery cloth to remove them.
5. Check the lubrication hole and gallery in the engine block and idler hub for blockage.
   1. If the lubrication hole is blocked, clear the lubrication hole.
   2. If the lubrication hole is not clogged, no cleaning is required.
6. Inspect the bushing contact surface of gear and bushing assembly for signs of scoring, discoloration due to overheating, or excessive wear.
   1. If the surface of the bushing is not acceptable, replace the gear and bushing as an assembly.
   2. If the surface has no damage, reuse the bushing assembly.
7. Measure the clearance between the bushing and hub.
   1. If the clearance is more than 0.033 - 0.076 mm (0.0013 -0.0030 in.), replace the gear and bushing as an assembly.
   2. If the clearance is to specification, 0.033 - 0.076 mm (0.0013 -0.0030 in.), reuse the gear and bushing assembly.

Section 1.31.3
Installation of Adjustable Idler Gear Assembly

Install the adjustable idler gear as follows:‪

1. Coat the contact surfaces of the hub and idler gear bushing with clean engine oil.
2. Install the idler hub, with the Part Number facing outward, to the studs in the gear case with the locating pin in the idler hub towards the gear case. See Figure "Idler Hub and Related Parts" .
   

   1. Gear Case‪	3. Stud Bolt‪
   2. Idler Hub‪	4. Stud‪

   Figure 4. Idler Hub and Related Parts

3. Install the adjustable idler gear with the Part Number facing outward, and install adjustable idler gear hub retaining plate.
4. Install three nuts onto stud bolts and finger tighten.
5. Install the bull gear and camshaft idler gear assembly Refer to "1.32.3 Installation of Bull Gear and Camshaft Idler Gear Assembly" .
6. Install the gear case cover. Refer to "1.11.3 Installation of Gear Case Cover EGR Model" .
7. Install the camshaft gear assembly. Refer to "1.26.5 Installation of Camshaft Bearings and Camshaft Gear Assembly" .
8. Adjust the gear lash between the adjustable idler gear and camshaft drive gear. Refer to "1.25.2.2 Engine Timing for the Compact Gear Train Assembly" .
9. Torque three idler gear nuts previously installed to 103-113 N·m (76-83 lb·ft).
10. Install any other components that were removed for access to the gear case cover.
11. Refer to "12 Operation and Verification" for verification of proper camshaft drive gear installation.