i've tried your technique---gear oil was too thick to 'gravity-fill' with the small hosing. i have two different pumps pictured above. in the end, sometimes its easier to just cut the tip off the top of the oil container, aim it in the fill hole, and squeeze. it can be a tight fit to get the oil container near the fill hole, but i will even empty half the oil container first, and scrunch it up a bit to get it into place---its quick, easy, and doesn't 'gunk-up' one of the pumps that you will have to later clean