Can you tell me what would cause the toilets to gurgle when the washing machine drains?

Can you tell me what would cause the toilets to gurgle when the washing machine drains?
This happens when the disharge from the washer has insignificant air enough to vent it so it vents, (draws air in) through the toilet bowl. The sound you hear is the air being sucked through the toilet bowl. The solution would be to snake the washer roof vent. Good luck, Tom

Tom nailed this but you probably need a bit more direction. Your vent stack is best rodded from the roof. Use enough rod to reach roof to basement floor plus 15' more. Hope you don't have a 12/12 roof.