TM 5-3805-255-14
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ADJUSTMENT CONTINUED
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4. Apply Prussian Blue Compound (WP 0130, Item 8) to ring gear teeth (Figure 32, Item 1). When gear is rotated,
Prussian Blue Compound is squeezed away by contact of teeth leaving an imprint the exact size, shape, and
location as gear contact.
5. Sharper impressions may be obtained by applying a small amount of resistance to ring gear with a steel bar
and using a wrench to rotate pinion. When making adjustments, check drive side of ring gear teeth (Figure 32,
Item 1). Coating approximately 12 teeth is sufficient to check tooth contact.
Figure 32. Prussian Blue Compound Application.
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6. With adjustments properly made, contacts like those shown in Figure 33 will be obtained. Area of contact
should favor toe and is centered between top and bottom of tooth.
7. After a satisfactory tooth contact pattern is obtained, especially in relation to top and bottom of the tooth,
backlash may be altered within recommended limits of 0.008 to 0.015 in. (0.203 to 0.381 mm) to obtain a better
contact position relative to length of tooth. A high backlash setting can be used to keep contact from starting
too close to the toe. A low backlash setting can be used to keep contact from starting too far away from the toe.
8. Hand-rolled pattern shown in Figure 33 will result in a pattern centered in length of tooth when gears are under
load. Loaded patterns will be almost full length and top of pattern will approach top of gear tooth.
Figure 33. Correct Gear Contact Pattern.
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