you have something incorrect in your reassembly. no bearing should ride on threads.
if you don't already have them go to Binder Books and get GS1411 service manual and TC-37F parts manual at http://www.binderbooks.com/
in the meantime, you can view these publications at http://www.cleancomputes.com/Cub/index.html
the parts explosions and assembly instructions should solve your problem.
let us know how you make out