Shakes violently during spin cycle from back to

Just remove the transport bolts that hold the drum during transport. Instructions should tell you to do this

I had this problem with my front loader as well. It is probably the mounts or "level shocks" on the bottom of the unit under the tub. I have a Kenmore by Frigidaire and had to replace the "level shocks". I only paid about $43.00 and was not that hard to put on. Look under your machine and see if the shocks are connected to the tub. Check under the top panel also to see if that particular model has mounts up there too.