There’s only one way to completely replace all the oil in today’s automatic transmissions and that’s with a transmission flush machine. Fuller’s Automotive has the best one available, the MotorVac Transmission Flush Machine. First the oil is drawn from the transmission pan and we remove the pan and replace the filter and gasket as needed. The machine then fills the pan with new oil at which point we start the car and as the transmission sends old oil out the cooler line to be collected in the machine it is adding fresh new oil to the transmission. That way the transmission remains full of oil at all times during the service.
The lines going into and out of the vehicle’s transmission are clear so it’s easy to tell when all the old oil has been replaced. Why replace only 5 quarts of oil the old fashion way in a transmission that might hold up to 14 quarts total. With the cost of a new transmission today it only makes sense to replace the oil on a regular basis, especially if you do a lot of heavy hauling or towing.