The automatic transmission for motor vehicles includes a positive displacement pump, a sump hydraulically connected by a passage to the pump inlet, a line pressure control valve having a high pressure outlet, a passage carrying fluid from the control valve through a nozzle and an nozzle exit opening to the passage that connects the sump to the pump inlet. The high pressure passage has a cross section whose area decreases in the direction toward the pump inlet and terminates in a nozzle through which a high speed jet enters the low pressure passage through the nozzle exit opening.