Installed new fan motor on AC condenser and it is noisy. Checked for any mechanical rattles or rubbing and found nothing. Replaced motor again with another new one, same problem. I have done AC work for over 30 years what am I missing. Also replaced capacitor twice.

Also replaced capacitor twice.

Check size of capacitor being used. Incorrect size capacitor can make motor noisy.

Perhaps new motor requires different size cap than old.