What increases engine backlash?

Gear wear is the correct choice as it directly contributes to increasing engine backlash. Backlash refers to the slight movement or play between meshing gears, and it is a normal condition that can occur as gears engage and disengage. However, as gears wear down over time due to normal operational forces, the fit between the gears can become looser, resulting in increased backlash.

When gears experience wear, the tolerances that maintain their tight fit diminish, allowing for greater movement between them. This can lead to operational inefficiencies, increased noise, and potential damage to the gears if not addressed. Regular maintenance and monitoring of gears play a key role in managing backlash and ensuring the longevity and performance of the engine.

The other options, while they may contribute to mechanical issues, do not directly relate to the specific increase of backlash in the same manner as gear wear. For example, poor lubrication can lead to increased friction and heat, which may affect gear performance, but it does not inherently increase the gap created by wear. Excessive load can strain gears but does not change the inherent design fit, and improper alignment affects overall efficiency and wear patterns, not specifically the backlash itself.