[rotorwrench]

If it has to come apart for any specific reason, ie, noisy, metal in oil, or any other detectable problems then it should go through a full disassembly inspection. Note gasket shim packs for reassembly during initial tear down.

A person shouldn't be too quick to replace bearings unless they show excessive wear or damage to rollers. If it looks good, it likely is still good. If bearings on one side are bad then replace the other side as well whether it's pinion shaft or differential carrier. Same with gears. If they look bad, replace them otherwise just continue them in service but keep in mind that it's not a good idea to set up used bearings with maximum preload and used gears with minimum backlash. Set the used stuff a bit on the loose side but still within specs.

If there is no problem with it then put a leever on it and leever alone.