Final answer:
During a hub adjustment with a drive-on type dust cap, the dust cap, wheel bearings, and seals are often replaced due to potential damage or wear during removal. Inspection of the spindle, hub, and retainer rings is also advisable.
Step-by-step explanation:
When doing a hub adjustment on a vehicle with a drive-on type dust cap, certain components typically need to be replaced to ensure proper function and safety. These components usually include the dust cap itself, because once removed it may not fit as securely, which could allow for contamination of the hub assembly. Additionally, it's often necessary to replace the wheel bearings and seals, as they can be worn or damaged during removal, and thus might not provide the necessary smooth operation or sealing once reinstalled. It's important to also inspect other related parts such as the spindle, the hub, and the retainer rings for any signs of wear or damage whenever performing a hub adjustment or maintenance.