Whether to use single or matched pair to replace worn gear?
For standard cylindrical gears (spur or helical), single-gear replacement is generally acceptable provided the mating gear is in good condition.
However, for spiral bevel or hypoid gears, we strongly recommend replacing the pinion and ring gear as a matched pair. This is because bevel gears are manufactured as a set with a unique contact pattern and lapping relationship. Replacing only one side of a bevel pair often results in incorrect contact patterns, increased noise, rapid wear, and premature failure. If a customer insists on single-gear replacement for cost reasons, we require the mating gear to be shipped to us for inspection. We will then measure its actual geometry and attempt to manufacture a matching counterpart, but we cannot guarantee the same noise and lifespan as a factory-matched set. We always document the risks in writing before proceeding.