Different way to change tranny fluid?

[chefofamore]

While installing the transmission cooler for a honda trailer, I wonder if the following method would replace most of the fluid rather than drain and filling method.

Simply put the return line in the transmission cooler to drain while adding fresh fluid into the dipstick hole.

May be a two person procedure but if you continue to add new fluid until you see clean fluid would replace old stuff in torque converter as well, don't you think?

Of course the car should in running in park or neutral and occasional shifting with a foot on the brake would help as well.

What do you think?

[ctobio]

Bad idea.

You cannot pour fluid fast enough to keep up with the fluid pumping out of the cooler line. This would be a very bad thing.

[mfisher1967]

Some folks run the engine for a few seconds with the transmission cooler's return hose disconnected. They let about 2 quarts drain into a bucket that is marked to allow for accurate measurement, shut off the engine, add the same amount of new fluid to the transmission and repeat the process until all new fluid is present in the system.

I have two issues with this practice. First, this job requires two people, one to watch the fluid drain and one to shut off the engine in a very timely manner. Second, anytime hoses are removed there is a chance that leaks will occur, or the hose may slip off the barb at some point down the road. Some will say the chances of this happening are small, but Murphy's Law seems to get me every time.