As the washer attains higher spin speed there is a rumbling that seems to be coming from the rear. I checked the drive pulley in back, belt and motor and nothing seems like bearings are loose. It seems to be coming from within the "outer tub" from the back. If it was the bearings and I took off the drive pulley (big ~14" dia wheel in back) wouldn't a test of the bearing to see if by grabbing the shaft and shaking it I would feel some "play"? I do not, everything seems tight. As I listen it doesn't seem to be coming from where the inner tub shaft comes through the outer tub in the rear but more from inside the outer tub and more toward the rear of the unit. Shock absorbers, springs, etc. all look fine. Otherwise all is working with the unit. Any ideas are appreciated.