The Automatic Transmission Flush Explained

Automatic transmissions are extremely complicated, and they need to operate at peak performance for your car to shift smoothly and properly. Keeping the transmission fluid clean and fresh is one key to extending the life of your automatic transmission. Like engine oil changes, the fluid in your transmission must be changed at regular intervals. Many car owners have no idea what this service entails nor how much it will cost. This article will help explain both.

The Transmission Flush Process

If you have never heard of this before, you might be wondering, “What is a transmission flush?” Quite simply, this is a way to remove the old fluid from your transmission and refill it with fresh, clean fluid. This varies from a simple fluid drain and change for a few reasons. First, draining the fluid from the transmission only removes about 60-70% of the old fluid. Much of the old fluid remains inside the torque converter and other components, so gravity alone is not enough to remove all the old fluid.

However, a proper fluid flush removes all the old fluid from the transmission. When a flush is performed, special equipment is connected to the car’s transmission. It uses either a vacuum type pump or the pressure from the transmission itself to push the old fluid out of the system. As the old fluid is removed, new fluid is pumped into the system.Your transmission is now filled with completely new fluid to help protect it from heat and friction.

How Often Should a Flush Be Performed?

The answer to this question depends on what type of car you own. Always consult your owner’s manual for the manufacturer’s recommendation on service intervals. Some vehicles require a transmission flush every 30,000-40,000 miles while others only require this service every 100,000 miles. Waiting too long to perform this service could have serious consequences, but there is no need to waste money performing it too often either.

Even if you are not at the recommended service interval yet, if you are experiencing any automatic transmission issues, then you might consider doing a transmission flush. Many times, a simple flush can help to correct shifting or slipping issues without breaking the bank. Always consult a qualified mechanic to help diagnose the problem, but a flush is an easy thing to try before tearing apart the transmission.

Can a Transmission Flush Be Harmful?

This is a highly debated topic, but the general consensus seems to be this. If you have gone far too long without performing your transmission service, then a flush might not be the best idea. Flushing your transmission at that point could potentially push metal shavings and debris into parts of your transmission where damage could be caused. In that case, a simple drain and refill might be your best bet. However, if a transmission flush is performed at the recommended intervals, then there is very little chance that it will be harmful to your car.

If you decide to drain and refill instead of flushing, then most mechanics recommend performing another drain and refill in 10,000 miles. This will help to get even more of the old fluid out and refill with clean fluid. These back-to-back fluid changes will help to extend the life of your transmission without taking the risk associated with a transmission flush of an older transmission.

How Much Does a Transmission Flush Cost?

Luckily, a transmission flush is a relatively inexpensive repair. On average, you can expect to pay $250-$400 for a transmission flush. Most of the cost comes from the transmission fluid itself. Modern transmissions can require 16 quarts or more of fluid to refill. At several dollars per quart, the fluid alone will cost over $100.

While this is not an extremely expensive repair, some people do not have a few hundred dollars sitting around for a car repair. Instead, you might opt to sell your used car and get some money in your pocket for it. Many car buying services will purchase your vehicle regardless of its condition, so they will still pay cash even if the car has transmission problems.


Automatic transmissions require regular flushes or fluid changes to continue operating at peak performance. This service is relatively inexpensive and should be performed at regular intervals following your manufacturer’s recommendation. While a flush will cost a couple hundred dollars, this is a fraction of the cost of a transmission rebuild or repair. If it is time for a service or you have any transmission problems, talk to your mechanic about performing a flush of the system today. It might just save you an even larger repair bill down the road!

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