Transmission Flush Service and Power Purge

Automatic transmission flushes and power purges are often a waste of money and can even be detrimental to the health of the transmission. For many years, this type of transmission fluid service has been shamelessly marketed to car and truck owners as a fix for automatic transmission problems. For the record, a transmission service will never, ever, repair or undo the wear or damage within an automatic transmission that is causing it to malfunction. Furthermore, it cannot eliminate the effects that the wear or damage has on the operation of the transmission. Replacing the old fluid with new can have benefit, as it will occasionally reduce the adverse effect that the underlying transmission problem has on the operation of the transmission, but this only helps for very specific types of problems, and then usually only for a few months. Keep in mind that any type of transmission service replaces some, but not all, of the transmission fluid, because the torque converter is completely filled and cannot be fully drained in its installed position. If it has been determined that an automatic transmission fluid change will buy you some extra time, you should consider it, but steer clear of the power purge service.

Flush and Power Purge Not Recommended

We strongly recommend that you avoid anything marketed as a transmission flush or power purge, and choose to service the automatic transmission fluid using the drain and fill method, by dropping the transmission pan if necessary. At its best, a transmission flush or power purge does nothing more than changing out some, but never all, of the transmission fluid. In many cases, however, it can do much worse. Many of these power purge flush machines use a diaphragm to force the new transmission fluid in as the old comes out. These diaphragms have seals which can leak over time, thereby allowing old fluid to reenter your transmission along with the new. Even worse, it may allow metal particles and other debris from many other customers’ vehicles to contaminate your vehicle’s transmission. Moreover, transmissions contain magnets to collect any metal that may have accumulated over time in the pan. With a flush or power purge, this metal will be dispersed throughout the transmission, possibly causing damage.

Fluid Service Interval

Automatic transmission fluid services and changes are specified by the vehicle’s manufacturer. Unlike motor oil, automatic transmission fluid can provide many tens of thousands of miles of service before a transmission service or a fluid change is required. Engine oil breaks down more quickly because the air that is constantly pumped through an engine oxidizes the motor oil at an accelerated rate. Gasoline as well as the byproducts of combustion also contaminate motor oil and reduce its effectiveness as a lubricant. Automatic transmission fluid does not experience these conditions, so lasts much longer. Changing the transmission fluid can create leaks and may lead to other problems if not done properly. It can also be expensive so should not be done needlessly or in cases where it does not produce a positive result. Upgrading to a fully synthetic transmission fluid is a viable option for use in harsh conditions but the specific type should be properly chosen.