Drive gears and pinions are tested and marked at the time of manufacture to detect machining variances and to obtain desirable tooth contact and quietness. This procedure is performed to

• A. Obtain gear teeth angles
• B. Show the correct part number listing
• C. Show where tooth contact is quietest
• D. Designate the specific rear axle for their use

Answer: (C)

The main idea is to ensure a smooth, quiet gear mesh by checking the actual tooth contact pattern and adjusting for manufacturing variances. Gears and pinions can have small differences from perfect geometry, and marking them during manufacture lets technicians see where the teeth actually touch when the parts are brought together. By identifying the contact pattern, they can orient and align the pair so the load is shared evenly across the tooth faces and the contact is centered rather than biased toward the toe or heel. This leads to the quietest, most reliable operation in service. It isn’t about determining gear angles, listing part numbers, or designating a specific rear axle. The purpose is to locate the tooth contact that yields the quietest, most even mesh.