2004 Electric Motor Grinding Noise

[Billtco]

Hi, Guys, New to the forum and this is my first post. The motor makes a grinding noise when running. I took the motor apart and found a loose bolt inside( it didn't belong to the motor) cleaned up the armature, checked and lubed the bearing and sprayed stator and amature with electra-clean. Put it back and it still has the same noise. I know it is in the motor cause it make the noise with the motor off the differential. The cart runs at normal speed and nothing seems to be dragging. The only problem I found was a little rust on the rear bearing, but the bearing spins smooth and free. Any ideas?