Hondas torque convertors CANNOT be drained,, for the life of me i do not know why they did ( do ) not istall a drain plug on it as well..you are correct , the new fluid will mix with the old fluid,,, it is like doing an oil change and not replacing the filter ,the new oil will mix with the oil oil still in the filter ..
Honda does not reccomend flushing the transmission.. all they reccomend is that you do a drain and refill at the required maintanace schedule ,,it used to be 15k miles all the times on AT and 30k miles on Manual trannies on the older cars ,but now they say that you can wait longer,,,,,,,,,,,,,,,,For as critical as sensitive trannies are internally with all the valves, i would invest the 30 dollars and replace tranny fluid still every 15k or once a year ...make sure to use only Honda ATF-Z1 ,, it does make a difference over the regular DEXTRON III OR IV

some shops do a complete tranny flush where supposely they drain even the fluid in the torque convertor, i have never used a machine to do that,, so i cannot personally say how good of a job it does,,,,,,,,,perhaps another forum member that works at a shop that use that machine might be more familiar and have more info on that than i do ..but working at dealers for all those years all i ever did was a drain and refill as required by honda

 

Excellent Info guys ...I've got to Service the 03' V6 later this week..just Glad I don't have to let Honda rip me off.

Thanks