What might occur if the mainshaft clearance is excessive?

Excessive mainshaft clearance can lead to hard shifting in all gears primarily due to the loss of proper alignment and engagement between the gears and synchronizers. When the mainshaft has too much play, it can cause the gears to not mesh smoothly, resulting in a rough or difficult shifting experience. The increased clearance can make it challenging for the synchronizers to effectively engage the gear, leading to a situation where the driver feels resistance or grinding when attempting to shift.

This situation can affect all gears, not just a specific one, contributing to an overall hard shifting problem. The implications of excessive clearance can also affect the lifespan of transmission components as improper engagement might lead to additional wear and tear, which can compound the shifting issues over time.

In terms of the other options, while they may seem plausible in relation to transmission issues, they do not directly correlate to the effects of excessive mainshaft clearance in the same manner as hard shifting does.