What couild be causing the drain pipe fro washer to back up and spill all over floor behind washer

May be it's just a "suds lock." If the wrong type of soap is used (like dish soap) in a washing machine it makes too many suds. If it just started doing it and you haven't used any different soap it's probably gunk in the pipe.

It could be plugged with lint or junk from clothes that wouldn't fit through hose when spinning water out,turn off machine and take hose off back of washer, clean out with water or something you can put through tube and when cleaned out put back on washer, just an idea?

what couild be causing the drain pipe fro washer to back up and spill all over floor behind washer
Jack has the right idea. Lint and grease tend to bunch up and clog a washer drain line. The solution would be to snake the drain from the washer stand pipe or the washer roof vent. If using the roof vent put out enough cable to reach the base and 20 feet more Good luck, Tom

what couild be causing the drain pipe fro washer to back up and spill all over floor behind washer
You have a clog in the drain line that needs to be snaked out from the washer stand pipe or the washer roof vent. Good luck, Tom