You should perform a thorough external examination before the gearbox inspection port is opened. Use an inspection form to record important data that would otherwise be lost once cleaning is completed. For example, before cleaning the exterior of the gear housing, inspect it for signs of overheating, corrosion, contamination, oil leaks and damage. Measure the tightening torque of structural fasteners that carry significant loads such as torque arm bolts. Look for evidence of movement including cracked paint or fretting corrosion at structural interfaces. Note the condition of the fasteners and inspect load-bearing surfaces of components for fretting corrosion or other evidence of movement