Figure 3-106. Measuring Pinion Backlash.

TM 55-1930-208-24

3-51. SPEED REDUCER- Continued.

f. Reassembly - Continued.

CAUTION

The lower intermediate bearing rollers must be seated when measuring

dimension (B). Also exercise care not to displace the intermediate shaft

subassembly cross axially.

(17) Measure the intermediate helical pinion or shaft outside diameter with a micrometer, divide by 2 and

record as dimension (C).

NOTE

When measuring helical pinions with odd numbers of teeth, tightly wrap shim

stock (.010 inch minimum thickness) around pinion and measure the diameter.

Subtract twice the shim stock thickness from this value for the pinion outside

diameter.

(18) Add (B) + (C) and subtract total value from the pinion (MD) previously recorded. The difference is the

required high speed compressed shim pack. Select shims which total in thickness within + .000 inch to

.004 inch of the calculated shim pack.

(19) Remove the high speed head, add the calculated amount of shims and install head. Ti hten head bolts to

640 lb-in (62.80 Nm).

(20) Place a dial indicator (figure 3-106) against a bevel gear tooth at the gear outside diameter perpendicular

to the tooth surface.

(21) Rotate the bevel gear back and forth while holding the bevel pinion shaft immobile. Read the backlash

(tooth clearance) on the indicator. Required backlash is etched on the outer diameter of bevel gear.

NOTE

Final backlash at the mesh must equal etched backlash within .000 inch to +

.004 inch.

(22) To increase backlash, increase thickness of lower intermediate shim pack.

Figure 3-106. Measuring Pinion Backlash.

3-178