Which type of bearing usually requires preloading in a transaxle?

The requirement for preloading in a transaxle is most commonly associated with tapered roller bearings. Preloading involves applying a certain amount of force to the bearings to eliminate any excess clearance and to ensure proper contact between the rolling elements and raceways. This is particularly important for tapered roller bearings because they are designed to handle both radial and axial loads, and preloading helps maintain optimal performance and longevity by ensuring that the load is distributed evenly across the bearing surfaces.

In the case of tapered roller bearings, preloading enhances the rigidity and stability of the assembly, which is critical in applications like transaxles where precise alignment and load handling are necessary for effective operation. This careful setup minimizes play and vibration, leading to smoother operation and a reduction in wear over time.

Other types of bearings mentioned do not typically require preloading to the same extent. For instance, ball bearings and needle bearings generally operate effectively without the need for significant preload, and plain bearings rely on lubrication and surface interactions rather than a preload mechanism.