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Having owned many cars I read the owners' manuals which specify that transmission fluid should not be over filled. In every case when I have my transmission fluid changed by mechanics the level is always over full. This has not resulted in any leaks, that I know of.
Question: does it make sense to drain some fluid to bring it to the proper level?
Don't drain your transmission fluid, it's a bad idea to do it yourself unless you know exactly what you are doing, have all the right tools, and have a way to catch and dispose of any fluid properly. If you think there's a problem take it back to the mechanic and ask them to look at it.
If you aren't checking the fluid correctly then you will get an incorrect reading. On most cars you check it while the engine is running, usually in park (assuming it's an automatic transmission), and at normal operating temperature. You then pull the stick, clean it, put it all the way back in, then pull it out before reading it. If you read the level without cleaning it first then it will almost always over-read.
So read your manual for instructions on how to check your transmission fluid and then follow them to the letter. If you still get a reading of more than full then take it back to the mechanic for them to deal with.
