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I had the bearing replaced and it sounded much better, much quieter.

Now, about 3 months later, the motor is making the same loud bearing noise that it did before.
Not normal.....normally the motor bearing will outlive an EV and in most cases its owner. Something is wrong.

My questions are:

Could I have received a bad bearing?
Yeah, I suppose, but unlikely. However it may have been damaged from improper assembly.

Could the shaft be bent and put undue stress on the bearing causing it to be louder?
Ohhhhh! You got a bent shaft? I guess that is a question by you, not a statement. But get it checked.

Could the bearing be improperly seated in the front motor mounting plate?
I suppose.

Could the motor and trans be out of alignment to such an extent that the bearing is overstressed?
I suppose.

Could there be some other reason or cause for this bad bearing noise?
I suppose.

I am using a Lovejoy spider coupling with a plastic insert that should compensate for a small misalignment.
Cool. That can compensate for a few thou misalignment, but not a bent shaft.

To fix the problem, I've got to take most of the system apart. I would like to replace the bearing but I'm afraid that the new bearing will also fail.
Get your bent shaft fixed. And the rest of the system inspected and/or assembled by a machinist or professional.

Also, post up some pics.

Regards,

major
 

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There are 2 locating pins in my adaptor plate so once I have the motor and trans bolted, they will always be in the same relationship to each other.
Yeah, but in the right place?

The thought about a dial indicator is a good one. I'll have to try that when I take it apart.
Yeah, the dial indicator is a good idea. I'd say a must. And I'd try to use it before you dismount anything. See if you can verify what is in place now.

I have enclosed a picture with an arrow that shows the location of the lovejoy coupling.
I don't like the looks of that. I think it would be nearly impossible to keep concentricity and perpendicularity/parallelism to the necessary tolerance. And then the tailmount could be applying a bending moment which is stressing the bearing. Just speculation on my part. But I doubt if it was the fault of the bearing causing it to fail.

Another thing which is not visible on the pic is the DEH and bearing. Lubrication can be a factor with bearing failure. It is a sealed bearing? Is it open to the elements on the outboard side? Is it getting too hot? Things to consider. Normally motor bearings have 2 high temperature seals and are permanently lubricated with high temperature grease. This makes them cost more than the standard shielded std greased bearings. So, was the replacement bearing the correct one?

Regards,

major
 
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