It is important to inspect the bearings because they often provide clues as to the cause of gear failure. For example:
• Bearing wear can cause excessive radial clearance or end play that
misaligns the gears.
• Bearing damage may indicate corrosion, contamination, electrical discharge or lack of lubrication.
• Plastic deformation between rollers and raceways may indicate overloads.
• Gear failure often follows bearing failure.
Gear tooth contact patterns. (Complete this step before disassembling gearbox components for inspection). The way
in which mating gear teeth contact indicates how well they are aligned (Figure 1). If practical, record tooth contact
patterns under either loaded or unloaded conditions. For no-load tests, paint the teeth of one gear with marking
compound. Then, roll the teeth through mesh so the compound transfers the contact pattern to the unpainted gear. Lift
the pattern from the gear with scotch tape and mount it on paper to form a permanent record.
For loaded tests, paint several teeth on one or both gears with machinist’s layout lacquer. Run the gears under load
for a sufficient time to wear off the lacquer and establish the contact patterns. Photograph the patterns to obtain a
permanent record