from Goss’ Garage by Pat Goss

Modern automatic transmissions can trace their origins to an early gearbox from 1904 developed by the Sturtevant brothers of Boston. It was a clunky, inefficient, failure-prone gearbox that worked through centrifugal force. An unreliable, inauspicious debut and nothing like today’s transmissions which shift smoothly, deliver great fuel economy and provide exceptional durability. However, their amazingly sophisticated designs and electronic controls mean repairing or replacing a broken transmission today is more costly than buying an entire fleet of cars in 1904. Repairs usually start around a thousand dollars and replacement can run two to three thousand or more.

So with costs so high and prevention so cheap transmission maintenance makes a lot of sense. Basic maintenance used to include dropping the transmission pan, replacing the filter and refilling with fluid. But that was long ago and proper service has changed significantly because the old method can actually shorten rather than increase transmission life. That’s because the old method didn’t clean anything inside the transmission and you only replace about one third of its total fluid.

That process left the transmission as dirty as it was before the service and new fluid isn’t always compatible with the remaining old fluid. Because the transmission isn’t cleaned the new more-detergent fluid softens deposits causing them to move through the transmission leading to wear. These particles are so small they can pass right through a transmission filter but worse many modern transmissions do not have filters. In these applications the filter is replaced with material similar to very coarse window screen.

Today, proper transmission service is accomplished through flushing, which will drastically extend transmission life. A flush is nothing like the old fashioned fluid service. In a flush there are cleaning chemicals installed into the transmission. Once the cleaners are installed the car is run to circulate them and dislodge all the yucky stuff that has built up inside the transmission, torque converter, cooling lines and transmission cooler.

Throughout this process the car is connected to a transmission flush machine and every drop of fluid that circulates back into the transmission must first pass through the flush machine’s very efficient bank of filters. That way all the bad stuff is quarantined outside the car preventing damage. Once the cleaning is done the machine installs new transmission fluid.

A flush should be done every two years or 24,000 miles never more than 30,000 miles. When it comes to the fluids in your car there is nothing more beneficial than cleanliness. Also contrary to what your dealer may have told you there is no such thing as a fluid that lasts the life of the vehicle. Nothing lasts forever, all fluids wear out and when the fluid wears out the transmission soon follows. There is also no such thing as a completely sealed transmission, they can all be serviced in some form.

Finally beware of shops that sell you a fluid exchange and call it a flush. A fluid exchange is quick and dirty and highly profitable for the shop but a waste of your money. Fluid exchanges can be done in the service lane in about half an hour where a flush requires about an hour and a half. I know the economy is tight but avoiding preventive maintenance is truly a false savings. Metal doesn’t understand economics and if not kept lubricated fails and fixing a car after it breaks always costs a lot more than preventing the failure through service. Also shop carefully as business is horrible and many of us are barely hanging on. Desperation sometimes pushes good people to do bad things.