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Transmission Flush: Is It Worth It?

What is a Transmission Flush-?

A transmission flush is a shop service that flushes out all the old transmission fluid and replaces it with fresh fluid. The special government authorized equipment is needed for this service. In some cases, the filter, cooler lines, and pan gasket are also replaced. Because this service can prolong the life of your transmission in the same manner as an oil change, trans. flush service may be recommended every 30,000 miles, depending on the manufacturer.


Average Cost of a Transmission Flush

The average cost of flushing your transmission is $150. But, you can expect to pay double this price if you have a high-end model or have the service done at the dealership. A number of factors are weighed to determine the costs of service to your vehicle because they all have different hourly flat rate labor guidelines. These guidelines provide a benchmark of how much time the repair should take in the ideal situation.


Price Assessment Factors

  • Location: The cost of living and services in some areas is naturally higher. NYC compared to Delaware where there are no taxes will naturally see a large variation in total prices.
  • Year, Make, and Model of the Vehicle: An older domestic vehicle like a Ford that has a small engine and easy access to the transmission and oil lines will likely be cheaper to service than a vehicle with a high-end Audi with a turbocharged engine and difficult-to-access transaxle.
  • Shop Type: A quick lube shop that exclusively works on flushes will likely have better rates than a dealership or independent mechanic.
  • Fluid Type: There is a wide range in the quality and price of fluids used. The options can be either expensive fluid that is only sold by the dealership, universal synthetics, synthetic blends, or conventional fluids like Dextron III or Mercon V.
  • Flush Machine Type: The machines flush the fluid at the pump inlet or cooler lines. Some use additional pressure and are called power flush machines.
  • Number of Quarts Required: A vehicle may need more liquid than those required to fill a new transmission when the fluid is flushed because some services gradually dilute the fluid in the transmission and don’t fully remove it all at once.
  • Extras: If you want new oil cooler lines, a pan gasket, a new filter or need anything else related to the trans. flush completed at the same time, this will cost extra.


Effectiveness of a Transmission Flush

There are mixed opinions on whether a flush is good for transmission. This mainly comes down to the quality of the service and the type of service used on a particular model. Many transmissions today come as sealed units that are supposedly filled with a lifetime transmission fluid that is designed to last the life of the vehicle.

Audi, Volkswagen, BMW, Mazda, Kia, Hyundai, Cadillac, Subaru, Chrysler, Chevy, Lincoln, Saturn, Toyota, and many more are making models with sealed transmissions. The theory is that by the time that the transmission fluid degrades enough to be noticeable, the life expectancy of many other parts of the vehicle are likely worn out also.

Most of the time that a sealed transmission unit has new fluid added, it is because there is some inadvertent event that caused other components to degrade prematurely. These can be broken connections to the valve body or other electrical sensor problems that require repair and the addition of fresh fluid at the same time.

The Germans are very refined about engineering the highest quality synthetic lubricants like Elf motor oil that is required as mandatory maintenance to retain the factory warranty in many of their turbo diesel vehicles. It is not hard to believe that they would engineer a superior synthetic oil that would never need to be flushed for the life of the transmission.

At a certain point, the clutch packs and seals inside of the transmission will degrade from heat over time. Heat is the number cause of premature failures in transmissions as evidenced by the transmission developed by Ford for late 90’s Ford and Mazda models that did not have an oil cooler and was prone to overheating without this feature. Even the dealerships had no way of fixing them and could only warranty them for a year before they’d burn out again.

The reason why a lifetime synthetic fluid is possible to use in sealed transmission boils down to temperature. If the vehicles have an adequate heat exchanger, an oil cooler that will regulate the internal temperature, the heat should not have such a harsh effect.

Because synthetic fluids lack the paraffin waxes of conventional transmission fluids, they are more heterogeneous at a molecular level. They, therefore, remain at a stable temperature and are less prone to the effect of burning up in volatilization.

Although it would be beneficial if every transmission were filled with this type of high-grade premium synthetic transmission fluid, not every transmission is calibrated to operate on synthetic fluids.

The pressure and temperature setting for an ideal range of operation, as well as the tolerances between the various check valves and passages, may not function very well using a full synthetic in a transmission engineered for paraffin-laden dino oils.

The paraffin waxes create hotspots, burn up under heavy duty cycles, and degrade much faster over time.


Transmission Flush- Vs -Change

Although there are a few methods of flushing out the fluid in your transmission, it is different from simply draining and refilling the transmission with new fluid by dropping the pan. This is because most of the fluid is lodged in the deep internal parts of the transmission and may need to be tilted at a heavy angle to really get the majority of it out. Even then, you will not get all the contaminants out and less than half the fluid.

Flushing the fluid removes all the fluid or dilutes the fluid with many quarts of new fluid being pumped through the transmission to the point where residual traces of old fluid are negligible.


Transmission Flush-Process

There are different methods for flushing. The two most popular, hook up a machine to either the pump inlet or the oil cooler lines. When you use the oil cooler line method, the technician is simply hooking up a machine to the lines to feed in fresh transmission fluid and receive the old fluid through the other line. This is the most stress-free method because it does not change the pressures of the transmission or add anything too foreign that might damage its natural rhythm.

The pump inlet method involves removal of the oil pan and filter to pump all the fluid out of the transmission and to sometimes add a power flush of a cleaning solution. The machine is connected to the pump inlet directly and then drops into a collector from the bottom of the transmission. While this may be a more thorough cleaning, it also can risk damage to the delicate seals and stir up debris that jams up valves. A new filter and gasket are added at the end of the service.



As explained above, the fluids available may be highly specialized factory fluids, universal synthetics, universal synthetic blends, or conventional fluids like Dextron III and Mercon V.


How Often

As explained above, although a conventional oil flush may be recommended for every 30,000 miles, it all depends on the manufacturer and the quality of the transmission fluid.


Finding a Service Provider

When you are looking for someone to flush your fluid, you should always be sure that you find someone who knows exactly what your specific model needs. They should always change the filter after the service and pan gasket. Avoid power flushes and cleaning solutions that may cause more harm than good.

The oil cooler line method is probably the safest for any vehicle. Ensure that shop that you go to specializes in the procedure and that they are fully insured and experienced enough to work on your vehicle. For more information, you can contact us or call 318-742-7754.