let's settle this: change auto trans fluid?
 

This is by far the most divisive car related debate that I've had. Usually when it comes to these types of questions, you dig deep enough and you come to a fairly logical answer (idle warmup vs drive warmup).

But the definitive answer to whether or not it's better to change automatic transmission fluid still eludes me. I've had mechanics that I trust say that of course a transmission fluid change is a good thing. I've had equally knowledgeable mechanics say that no it's bad and that if you do get a change, don't flush the lines.

I've got the 09 sport Fit and I use the paddle shifter a lot. With this in mind I feel like maybe I should go ahead and get it changed. But then I don't want to end up ruining a great thing with my indestructible Fit....or maybe a fluid change is a good thing since I do want to run it into 300k+ miles.

Would you not change the oil in the car? No... Same thing about trans fluid.

Just do a drain and fill.

What I usually do, is drop the pan, measure how much fluid comes out, and then re-install the pan and add the same amount of new fluid. I do this periodically, depending on mileage, perhaps every couple years. I figure it gets out about half the old fluid each time. But this has been on various different cars I've owned. Not yet on the Fit, which is only at 34K miles.

I'm assuming the logic with this method is that you want to leave enough fluid in the transmission system so that it doesn't run dry on the initial startup after the change?

Well, not having done it yet on my Fit I have to admit I don't know. I'm used to regular American cars where you refill using the dipstick tube or the provided cap and there is never a dry start.

Drain and fill until it runs out of the fill hole.

Got it, thanks!

I have also heard old mechanic's tales of vehicles with 150K+ miles without an A/T fluid change which, upon getting a fluid change experience a catastrophic failure. One possibility is that the fresh, clean fluid caused a problem. The more likely explanation is that once you go 150K miles without an A/T fluid change you're living on borrowed time and just looking at the car cross-eyed could cause transmission failure.

As Frenzal suggested, I have trouble understanding the logic of not changing the A/T fluid when recommended. It's not all that difficult (on a Fit) and it's not all that expensive.

It is interesting that I am the only one so far that has voted for just a fill and NOT a flush (3 Yes votes, 1 Yes vote without a flush). I was under the impression that a flush was generally not recommended with our cars?

Yeah it is just a drain and refill situation. I misread the poll.

I do this "Noob" fill every 30,000 miles or so.

https://www.fitfreak.net/forums/2nd-...ill-flush.html

Same. My bad.

The only why I know how to "flush" an automatic transmission is to drain, fill, drive, drain, fill, etc. Which is just a waste of time and money.

I assumed they meant "flush" in this case as using the machine that forcibly flushes the transmission. My independent shop offered this at 100k miles, which I promptly turned down. A basic drain and fill for me, please.

See my reply just above yours for "noob" version of flush which avoids the waste

That is a good write up, thanks. I'll try that if I ever buy an A/T car.

Wouldn't the "Maintenance Minder" tell you when to replace the transmission fluid?