Car Doctor Q&A: Do You Change the Filter When Flushing the Transmission?

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Our resident auto service expert John Paul, the Car Doctor, answers a question this week about flushing the transmission on a Subaru Forester.

Q: My 2004 Subaru Forester now has 95,000 miles on it and it is due for a transmission flush (previously done at approx. 30,000 & 65,000 miles). There seems to be differing views as to whether or not the filter should be changed. My old records have faded so I can’t tell if the filter was changed on either of the prior tranny flushes. My quick change oil facility says don’t change the filter because it can only cause problems when the new filter is installed and they can suck almost all of the old fluid out. My mechanic says the filter should be changed to ensure a complete removal of old fluid. What is your opinion?

A: The recommend procedure is to drain the fluid using the drain plug in the transmission oil pan and replace the external “spin-on” filter. Although flushing the transmission fluid is a common procedure these days, draining the fluid and replacing the filter is the factory recommendation. As a side note Subaru doesn’t have a specific recommendation to replace the transmission fluid. The factory recommendation is to check and evaluate the transmission fluid every 30,000 miles. When it comes to flushing fluids, my recommendation is to follow the vehicle owner’s manual.

John Paul is public affairs manager for AAA Southern New England and a columnist for A certified mechanic, Paul tests dozens of new cars each year and also hosts a radio show on AM 950 and 550.

IMAGE SOURCE: Union Lube Shop


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