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Automatic transmission fluid replacement

Bill Thoms Jr

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The owner's manual for my 2004 Accord LX 4 cylinder automatic specifies draining and refilling the transmission fluid three (3) times at 120,000 miles for normal driving conditions, with a short drive between each refill. Yet when I checked with my local dealer they offered only to drain and refill once.


What is the proper way to service this trransmission? It's a one-owner car, always driven moderately. No problems with the transmission to date at 115,000 miles.

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As the manual states.


The transmission on your car is oriented in such a way that when draining the fluid you can only remove about 2/3 of the material in one drain. To fill it at that point would leave about 1/3 of the original (and likely dirty with accumulated metal shavings) fluid. When you go for a short drive the dirty fluid mixes with the new. At the next drain you are left with 1/6 of the original fluid and the third time you are left with 1/12 of the original fluid. When you are done you should have about 8% of your fluid as the original material which is what the factory deems as 'good enough'.


The dealer may try to charge you more. You can ask them to perform the service as described in the manual.


Nothing against factory service technicians, but for the most part they don't work on older cars. There are going to be individual techs with more or less experience but for the most part they do warranty service, not extending your vehicle life service. In my humble experience if you plan on keeping a vehicle significantly longer than 10yr/100,000 miles it is best to find an independent servicer you trust.

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