Just to add to my previous post…
Washing machines dump the largest amount of water flow at one time down a drain than anything else in a common house. Therefor, many times you can have no other problems whatsoever (sinks drain fine, toilets flush because they are not tied into that line but rather sweep into the main itself) but when you dump the washer it backs up in the floor drain. Very common. Snaking the washing machine line will clear it….one exception to this is if you have an older house, plumbed with say copper or galvanized lines….and you install a new “high capacity” washer. Sometimes these older lines don’t have the capacity to take the load the machine pumps into it. However, if you have always had the same basic kind of washer, and this problem is relatively recent, then a snaking it is.