Pentair Whisperflo 3/4 hp - Noisy Help!!!!

Here is what happened..... I had a new Whisperflo installed and everything was fine for a year. For some reason the motor burned up so I changed just the motor to save a few bucks. The pump now works fine but makes a whurring sound. The best I can describe it is rrrrRRRRrrrrrrrRRRRrrrrrRRRRrrrrrRRRRRrrrrrr.... I've isolated the noise and it was coming from the rear bearing in the motor casing. I changed it. Noise is still there!!! If i spray the bearing with WD-40, the noise goes away for about 4 hours then comes back. When I changed the bearing, the old one felt as tight as the new one that I installed.

Here's an added element to the issue... when the pump motor burned up, the impeller actually melted a little because the shaft got hot. I filed it flat again but can't be sure it's 100% flat. It may have a "wobble" of 1/64" if that. Could the impeller being "out of balance" cause the motor shaft/bearing to vibrate and make the sound that I described above?

Anyone else had that problem? Could the impeller being out of balance cause the issue?

Yes, a messed up impeller could definitely do it.

Replace the impeller, but also run the motor dry (disconnected, with no seal on it) to check for motor noise. Sometimes, bad motors are shipped. Be SURE to have someone put a foot on the motor, when it's powered on, to make sure it doesn't jump around. Those things have quite a bit of torque.