You mentioned a chirping sound at low speed? If you hold a stick to the machine and the other end to your ear you may be able to narrow down the location of the chirp. The fact that it got stiff to turn with the cover on tells me one of two things. Either the cover has something rubbing on it or tightening it down has warped the machine just enough to put pressure on something. Loosen up the cover and keep trying. You'll get it.
Rodney