Final answer:
Centering the steering gear establishes a neutral position, and aligning the front wheels in a true straight-ahead direction ensures accurate steering and prevents alignment issues. Thus the correct option is D.
Step-by-step explanation:
When adjusting the drag link length before installing it, it is essential that both the steering gear is centered (option a) and the front wheels are in a true straight-ahead direction (option b). The reason for this is to ensure proper alignment and prevent any steering issues once the drag link is installed.
Firstly, centering the steering gear is crucial because it establishes a neutral position for the wheels. This neutral position is the starting point for adjustments and helps maintain symmetry in the steering system. If the steering gear is not centered, it can lead to unequal steering responses and potential alignment problems.
Secondly, aligning the front wheels in a true straight-ahead direction is necessary to achieve accurate and balanced steering. If the wheels are not properly aligned, it can result in uneven tire wear, pulling to one side, and difficulty maintaining a straight path while driving.
The combination of both conditions, centering the steering gear and ensuring the front wheels are in a true straight-ahead direction, provides a solid foundation for the installation of the drag link. This ensures that the steering system operates smoothly, promoting vehicle stability and handling.
In summary, adjusting drag link length with the steering gear centered (option a) and the front wheels in a true straight-ahead direction (option b) is crucial for optimal steering performance and overall vehicle safety.