LEEVENSPARK

Crown Wheel Preload To achieve the low noise level, housing rigidity and accurate gear alignment are essential with a hypoid gear. This necessitates elimination of slackness in the crown wheel bearings by preloading. Out of the various methods used to measure the preload, the most common one is to measure the spread (outward deflection) of the bearing caps when the adjusters are screwed together. As an example, a preload cap-spread of 0.1 mm indicates that after preloading the side bearings, the distance between the bearing caps has increased by 0.1 mm.                                                                   Fig. 26.42. Final drive adjustment When shims are employed to control the backlash, the preload is obtained by increasing the shim thickness on each side of the crown wheel and the shims are added after the backlash has been set. Axles with this construction need a special tool to 'spread the caps' before the crown wheel assembly is removed or refitted. Figure 26.

Crown Wheel Adjustment After setting the pinion, the crown wheel is installed in the assembly. The correct bearing cap must be used during this operation, as these are not interchangeable. Backlash is adjusted at this stage by moving the crown wheel towards or away from the pinion. Prior to the final measurement of backlash with a clock gauge, it is necessary to ensure that the crown wheel run-out is within the recommended limits. Meshing of the gear is checked by applying a smear of marking compound to the driving side of a few crown wheel teeth and then turning the pinion in the direction of rotation while applying a resistance to the crown wheel. The marking thus obtained indicates the mesh of the gears with respect to pinion position and backlash. Figure 26.41 illustrates the change, in relation to the correct marking, when the pinion position is changed.  A 'correct' marking indicates only a limited contact between the teeth under light-load test conditions. But if full lo