Dave Wilkes Transmissions Pan-Off Flush Service
If you are going to change the fluid in the transmission it only makes sense to change all of it not just half of it. Flushing the transmission with the pan off is the best way to do that. This is a brief, simplified explanation of that process.
Basic Fluid Circulation
The fluid in the transmission is in two areas, the pan and the torque converter. When the motor is running the normal circulation begins at the suction side of the pump, which draws the fluid from the pan through the filter. Then the pressurized fluid goes into the torque converter, through the transmission cooler lines to be cooled. Then the fluid goes through the transmission and falls back into the pan.
Pan Service
When the pan is removed this drains about half of the fluid and allows us to inspect and clean the pan and change filter, (some transmissions have a screen that isn't replaced), and the pan gasket,(some transmissions have a molded pan seal that is not replaced unless damaged or leaking).
Pan Off Flush
The other half of the fluid stays in the torque converter. Most torque converters don't have a drain. We replace the fluid in the torque converter by connecting a machine (Trans-Action 2.0)
that provides new fluid to the transmission pump then we start the engine. With the engine running and using the normal fluid circulation, new fluid is circulated through the torque converter, transmission cooler & lines, through the transmission and clutch packs. Then the old fluid leaves the transmission while the pan is off and does not mix with the clean fluid being added. The machine does not force fluid through the transmission, it simply provides new fluid to pump so the normal circulation does the flushing. We normally flush using 2 gallons of fluid while the pan is off. We are the only ones I know of in Ventura that performs a "Pan Off Flush."
Pan On Flush
The most common flushing method at other servicing facilities, repair shops, fast lubes, and dealerships is done with the pan on. A cooler line is disconnected that goes to the transmission cooler in the radiator.
When the motor is started the old fluid leaves the transmission through the pressure line into the machine and then the machine adds fluid through the return line. The new fluid then enters the transmission and mixes with the old fluid in the pan. The filter is not replaced and with the new fluid is diluted by the old fluid that is in the pan. This is significantly less effective method of flush as our "Pan Off Flush."
