I've heard the same. It is possible, but this mostly applies to cars with automatic transmissions. The theory is if it hasn't been changed in a while and there is a lot of gunk in the tranny, going to place such as Valvoline that uses a pressurized system to force out the old tranny fluid and force in the new could plug your filter with all that old gunk, and cause problems. The best way to change the tranny fluid on most cars is to drop the tranny pan and replace the filter while you're at it. I have never changed the fluid on an auto honda tranny though so I really don't know what to say specifically about them. Are you doing this to a honda?