3406E and 3456 Industrial Engines Testing and Adjusting – Gear Group (Front) – Time

Static Check of the Timing Gear Position

Illustration 1 g01106267
Front gear group

(1) Timing marks

(2) Camshaft gear

(3) Adjustable idler gear

(4) Idler gear

(5) Cluster gear

(6) Timing marks

(7) Crankshaft gear

(8) Oil pump gear

The correct fuel injection timing and valve mechanism operation is determined by the alignment of the front gear group timing. Timing marks (1) and timing marks (6) are aligned in order to provide the correct relationship between the piston movement and the valve movement.

Required Parts

Table 1
Part Number Description
374-3473 (1) Gear Segment Tool
421-7202 (2) Gear Segment Tool
( 1 ) For use with the 130-4701 Gear As
( 2 ) For use with the 361-8238 Idler Gear As

Setting Backlash for Camshaft and Adjustable Idler Gear

Note: The rocker arm bolts must be loosened to remove preload from the camshaft.

Illustration 2 g02685416
Front cover is removed.

  1. With the front cover removed, remove bolts (3), plate (2), and adjustable idler gear (1) .

  1. Loosen one bolt and two nuts (4) that secure the stub shaft. Remove the remaining three nuts. The one bolt and two nuts (4) can still be accessed when the gear segment tool is installed.

Illustration 4 g03320498
(5) Timing marks

(6) 374-3473 Gear Gauge

  1. With the flywheel pinned at TDC for cylinder one, align timing marks (5) .


  1. Install the cam gear backlash tool onto the stub shaft, as shown. Both sides of the gear segment tool should be engaged with the corresponding gear, as shown. Hand tighten the one bolt and two nuts enough so that slight resistance is felt if the stub shaft is rotated.

  1. Measure the backlash between camshaft gear (2) and gear segment tool (3). When the gear segment tool is held stationary, the backlash between the gears is 0.356 ± 0.254 mm (0.014 ± 0.010 inch). Lightly tap the stub shaft with a soft mallet to move the gear segment tool closer or further away to the cam gear as necessary. This movement will increase or decrease the amount of backlash.

  1. Once the proper backlash is obtained, tighten the nuts and the bolt (4) to a torque of 55 ± 10 N·m (41 ± 7 lb ft).

  1. Remove the cam gear backlash tool.
    1. Clean the studs with a wire brush to remove any old thread lock compound for the three nuts and washers removed in Step 2.


    1. Apply Loctite 242 to the studs.


    1. Install the 3 nuts and washers that were removed and torque to 55 ± 10 N·m (41 ± 7 lb ft).


    1. Remove the bolt, two nuts, and two washers that were tightened in Step 6.


    1. Clean the bolt and two studs of any old thread lock compound using a wire brush.


    1. Apply Loctite 242 to the bolt and the two studs.


    1. Install the bolt and two nuts with washers. Torque the bolt and nuts to 55 ± 10 N·m (41 ± 7 lb ft).

  1. Install idler gear (1). Verify that the correct amount of backlash is still correct. The mark on the camshaft gear should still align with the mark on the front housing.


  1. Install plate (2). Before installing bolts (3), clean the bolts with a wire brush to remove the old thread lock compound. Apply Loctite 242 to the threads of the bolts and install the bolts. Then, tighten to the proper torque.


  1. Install the front cover. Refer to Disassembly and Assembly, “Housing (Front) – Install”.


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