Manual Transmission Gear Oil Pump This is a pump that will fit on a bottle of gear oil and allow you to fill your manual transmission. Easiest way to fill your manual transmission. You have to fill from the side of the transmission in a small hole. It is almost impossible to do this just by using the bottle to squirt it in, you will spill half of your oil doing it that way. With this pump you can sit the bottle on the floor and just pump the oil in without the fuss or muss.