Why should you NEVER use a metal hammer to install bearings on the final drive?

You should never use a metal hammer to install bearings on the final drive because it can cause significant and often invisible damage to the bearing's internal components, leading to premature failure. Bearings are precision components designed to operate with very tight tolerances. The internal components, such as the balls or rollers and the raceways, are hardened to resist wear. However, they are also brittle and susceptible to damage from impact loads. Using a metal hammer to directly strike the bearing can transmit shock loads through the bearing, causing indentations or cracks in the raceways or damaging the rolling elements. Even small indentations or cracks can create stress concentrations that will lead to accelerated wear and eventual bearing failure. The damage may not be immediately apparent, but it will significantly shorten the bearing's lifespan. Furthermore, using a metal hammer can also damage the bearing seals, allowing contaminants such as dirt and moisture to enter the bearing, further accelerating wear. The correct method for installing bearings involves using a bearing installation tool or a press that applies even and controlled force to the bearing's outer race. This prevents shock loads from being transmitted through the bearing and ensures that it is properly seated in the housing. If a bearing installation tool or press is not available, a soft-faced hammer (such as a rubber or plastic hammer) can be used, but only in conjunction with a bearing driver that matches the bearing's outer race diameter. The bearing driver distributes the force evenly across the outer race, minimizing the risk of damage. Therefore, using a metal hammer to install bearings is a practice that should be strictly avoided to ensure the bearing's longevity and reliability.