Thank you for your reply. Now that I listen more closely to the entire cycle, I find that the sound is more of a groaning (not squealing). It happens with every revolution of the tumbler, during wash and during rinse/spin. The groaning is quite loud as the tumbler begins to move. It's present as the spin cycle starts, then gets higher in pitch as the spinning speed increases. Once the spinning speed is very high, the groaning seems to disappear.
Does this change your diagnosis?