My Dryer before I started to work on it squealed almost continuously. I believe I correctly assessed that the problem is the support rollers and so I bought the maintenance kit for the dryer. When looking at the drum in relation to the bulkhead (back of dryer), I noticed that the little seal would get pinched and un-pinched as you turn the drum.
So I removed the old stuff, followed the kit, oiled up the supports and the wheels, replaced the wheels, replaced the belt, replaced the idler pulley with one that has a wheel, and then put everything back to where it was. Problem is, when I turn the drum, it is still moving from front to back almost cyclically despite replacing the support wheels which go on the support shaft. So before I installed these support wheels, I noticed that the shaft in one part looked a little scored but smooth and aside from that I didn't think too much of it because a replacement shaft wasn't part of the kit. So now I'm wondering, would that little scoring on the shaft(s) be the cause of the drum as you roll it move from front to back? It's either moving front to back or this drum is slightly angled and it just appears that way due to being unbalanced. I believe it was this very motion that caused the dryer to squeal continuously and therefore cause me to work on it.