If the bearing make noise, more play or hard points in ballrace, rusted, replace with new ball bearing..

I has some old model diesel engines with ball bearing from 1950 years, never replaced and in still good condition. These engines was stucked of castoroil, heated with heatpistol and used fuel to free up the engine. Then soaked in dieselfuel over night and feel as new engines. No rust cause the castoroil sealed the steel against rust.

Jens Eirik