Newer traction motors, both DC and AC, have improved gear case and motor support bearing seals. This was accomplished by enclosing the wheel, axle, gear, gearcase, and motor support bearings in a single, oil lubricated housing which bolts to the axle side of the motor casing. If a bearing goes bad, journal or motor support, the entire unit is removed and replaced with another because a wheel must be pressed off to change a support bearing. Amtrak replaces the motor support bearings as a matter of course with every second set of wheels mounted on the same axle.