safety of trans fluid pump out?

[brian3222]

07 accord automatic 2.4l
Ok we have all seen the videos of the pumping out of old trans fluid from the cooler line until its nice and red while running engine and filling trans with new fluid at the same time.

How safe is this? I know you have to keep pouring the new fluid in while the old is being pumped out. That make me a bit nervous.
1. If that tranny gets starved for fluid at all , well it aint gonna be pretty.
2. Or what about at some point for a moment or two having to much fluid in the system? You could blow a seal.
3. If you do , do this. What rate do you pour the new fluid in at?

Has anyone done this, this way?

What about this way ---- VS--- the old fill---run--drain x3 method?

thanks

[Jeff]

Don't do it. You're only supposed to do the 3x drain and fill method. Flushing the transmission out will cause many problems.

[nehonda]

I've done both and the cooling line exchange is not going to hurt the tansmission to run low (or high) on fluid for a few seconds at idle. If you see the flow stop, shut off the engine and add more ATF. It will pump fluid out faster than you can pour it in, so you dont have to worry about overfilling. I pump the old fluid into a container that has the quantity marked on the side so I know how much has been removed vs how much I'm pouring back in.

The advantage of doing the cooling line exchange vs 3 times method is you need less ATF. The 3 times method requires 9 quarts of ATF and you end up with about 86% new fluid since you are mixing with some old fluid each time. The cooling line exchange uses about 6 quarts and you end up with 90+% new fluid since you are pushing out the old fluid out instead of mixing it back in.

[Drew03Accord]

The way I see it, why take a chance? Once you do the initial 3x drain and fill, a single drain n fill every 20- 30K or so keeps the fluid fresh. As a matter of fact, I never performed a 3x drain n fill. I simply started doing the latter and changed the filter once.