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C3.3B Tier 4 Interim and EU Stage 3A Engines for Caterpillar Built Machines – Gear Group (Rear)

Timing Gear Backlash


Illustration 1g03007197

(1) Camshaft Gear

(2) Idler Gear

(3) Fuel Injection Pump Gear

(4) Crankshaft Gear

  1. Set a dial indicator (lever type) with the tip on the gear tooth.

  1. Move the gear to measure the backlash, holding the mating gear.

  1. If the backlash exceeds the allowable limit, check the oil clearance of the shafts and the gear.

  1. If the oil clearance is proper, replace the gear.

Table 1
Backlash between crankshaft gear and camshaft gear     New     C2.6 - 0.0400 to 0.137 mm (0.00157 to 0.00539 inch)
C3.3B - 0.0410 to 0.139 mm (0.00162 to 0.00547 inch)    
Allowable limit 0.22 mm (0.0087 inch)    

Table 2
Backlash between camshaft gear and idler gear     New     C2.6 - 0.0460 to 0.136 mm (0.00181 to 0.00535 inch)
C3.3B - 0.0410 to 0.134 mm (0.00162 to 0.00527 inch)    
Allowable limit 0.22 mm (0.0087 inch)    

Table 3
Backlash between idler gear and injection pump gear     New     C2.6 - 0.0460 to 0.136 mm (0.00181 to 0.00535 inch)
C3.3B - 0.0410 to 0.134 mm (0.00162 to 0.00527 inch)    
Allowable limit 0.22 mm (0.0087 inch)    

Idler Gear


Illustration 2g03026036

(1) Idler Gear Mounting Bolts

Table 4
Tightening torque     Idler gear mounting bolts     C2.6 - 49 to 55 N·m (36 to 41 lb ft)
C3.3B - 30 to 34 N·m (22 to 25 lb ft)    

Side Clearance of Idler Gear


    Illustration 3g03007279

    (A) Side Clearance of Idler Gear

    (1) Idler Gear

  1. Set a dial indicator with the tip on the idler gear.

  1. Measure the side clearance by moving the idler gear to the front and rear.

    Table 5
    Side clearance of idler gear     New     C2.6 - 0.050 to 0.20 mm (0.00197 to 0.00787 inch)
    C3.3B - 0.15 to 0.25 mm (0.0059 to 0.0098 inch)    
    Allowable limit 0.90 mm (0.035 inch)    

  1. If the measurement exceeds the allowable limit, replace the idler gear collars.

Oil Clearance Between Idler Gear Shaft and Idler Gear Bushing


Illustration 4g03007376

  1. Measure the idle gear shaft outside diameter with an outside micrometer.

    Table 6
    Idle gear shaft outside diameter     New     34.959 to 34.975 mm (1.3764 to 1.3769 inch)    

  1. Measure the idle gear bushings inside diameter with an inside micrometer, and calculate the oil clearance.

    Table 7
    Idle gear bushing inside diameter     New     C2.6 - 35.000 to 35.055 mm (1.37795 to 1.38012 inch)
    C3.3B - 35.025 to 35.050 mm (1.3790 to 1.3799 inch)    

    Table 8
    Oil clearance between idler gear shaft and idler gear bushing     New     C2.6 - 0.025 to 0.096 mm (0.00098 to 0.00378 inch)
    C3.3B - 0.050 to 0.091 mm (0.0020 to 0.0035 inch)    
    Allowable limit 0.10 mm (0.0039 inch)    

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