Plumbing and Piping - Connect Washing Machine Drain to Main Stack

I have a 4" stack that goes from the basement all the way up through the roof. On the main floor, there is a toilet connected into the stack and then a sink & bathtub that have drains connecting together and then into the main stack via a Wye directly under where the toilet connects. Is it OK to put another Wye in the stack down in the basement in order to drain a washing machine? This Wye would be somewhere below the one that connects the tub/sink drains and would then have a trap before having the washer connected to it.
Thanks!

Yes, that should be fine.
I did the same thing in my basement.

Cutting in a drain as specified can be done and will most likely work just fine, but according to code a vent will also be needed someplace between the p-trap and where you go down to tie into the stack, or the stack itself. If a vent is not included, you may have issues when a toilet is flushed from above causing the trap to siphon.

Most codes allow the use of a mechanical vent known as a Studor Vent, or Air Admittance Valve (AAV). I personally prefer the use of a conventional vent system if possible because of the lack of moving parts to break down, but if it is not possible, use the AAV and you will be all set.

Thanks for the responses. I'll plan to do the wye and will look into using an AAV. I hadn't thought about the toilet flushing causing a siphon that would empty the trap but that makes sense. So I wonder if this means that my bathtub is technically not connected correctly since it drains into a p-trap and then runs over to the main stuck under where the toilet is connected but doesn't have its own vent (?)

Even though it is possible your tub may not be vented properly, there are many different ways to vent something on the same floor (branch interval), but I am assuming you are talking about putting the washing machine drain in the level below the bathroom, creating a new branch interval, requiring separate venting requirements.

I am not trying to over-confuse things here, but just explain that the tub may be vented ok even though it does not look like it.