If excessive tooth contact is observed in a hypoid gear set, which adjustment must be made first?

When excessive tooth contact is observed in a hypoid gear set, the optimal first adjustment is to move the pinion out. This action helps to correct the meshing of the gears, as moving the pinion outward can reduce the load on the teeth and improve the contact pattern, thus addressing any issues related to tooth interference or excessive wear.

Adjusting the position of the pinion can significantly alter the engagement of the gear teeth, allowing for better contact patterns that result in more efficient operation. Proper contact patterns are crucial to the longevity and performance of the gear set, and resolving issues quickly can prevent further damage.

While other options like inspecting the fluid, moving the ring gear closer, or checking alignment may be important steps in the maintenance process, they do not directly address the immediate concern of excessive tooth contact as effectively as adjusting the pinion position. Moving the ring gear or checking alignment could be subsequent steps if moving the pinion does not resolve the issue, but starting with the pinion adjustment is the most logical action to take in this situation.