Honda recommends only partial replacement of tranny fluid?

honda
odyssey

#1

I requested my mechanic to do a complete tranny fluid change on my 97 Odyssey yesterday but when I picked up the car, he had only drained and refilled, rather than use the machine that allows all the fluid to be replaced. They have done this complete replacement in the past but he claims now that Honda only recommends the drain and refill. This leaves a lot of the old fluid behind. He mentioned that it was undesirable to do so since the need to use Honda fluid was complicated as the machine has a large reservior. Was this the real reason, he didn’t want the hassle of dealing with Honda required tranny fluid or could it be that Honda doesn’t see the need to get out all the old transmission fluid?


#2

If you’re changing it periodically (say every 30k) a drain and fill is fine. You’re just replenishing spent additives, tranny fluid doesn’t undergo the more extreme service that engine oil sees, with combustion blowby contamination, etc.


#3

If you change it every 30K miles, then the partial change is okay. If you change it every 100K miles, then a full fluid exchange is needed. If you are changing it because of a transmission problem, it is probably already too late.


#4

The full fluid exchange is also known as a “Flush,” and Honda recommends against it for a very good reason. Flushes are a good way to hose a transmission.


#5

Actually has only been 25K but the time period according to the shop manual was due and it sees a lot of short trip, stop and go driving. Thanks for the advice, guess I’ve been wasting money on the full replacement the last couple of times.


#6

Trash the transmission? Is that true for other makes as well? Is it better just to go to a more frequent drain/refill cycle?


#7

30k is plenty frequent for drain/fill.


#8

I think so yes. The pumping of the flush can force contaminants into small passages where they can cause actual problems.


#9

If you use the transmission to pump fluid, you won’t damage it. But the high pressure flushing machines can damage your transmission. If they fluid is good and hot, almost all of it will drain out. I replaced almost all of the AT fluid in my Accord a couple months ago when I changed it.


#10

So maybe I need to learn to drain my own transmission fluid. Typically, is it similar to the operation for changing oil? Drain and refill to mark. Recheck after running the car?


#11

Its easier than changing your engine oil. Open drain plug, let drain, reinstall drain plug, refill using ONLY Honda fluid.

transman


#12

The drain and refill is fine. Don’t obsess about replacing 100% of the fluid.


#13

It can get a little more complicated than a simple oil change. Transmission fluid expands a lot when it gets hot, so it’s easy to overfill it, and in order to check the fluid, you have to get it up to operating temperature.

The last time I did a simple drain-and-refill on an automatic transmission, I overfilled it, drained some out, drove it around the block, and then checked the fluid. Then I added some fluid, drove it around the block, checked the fluid, and added some more. Then I repeated the process about five more times before I reached the full mark with the transmission and fluid at operating temperature.

I am sure after doing it a few times, you will know exactly how much ATF to put in, but the first time, schedule a lot of time to be careful, and measure the fluid carefully so you will know exactly how much you need next time.

Also, make sure you have a fresh crush washer for the drain plug.


#14

jaanni you were right…The shop owner didn’t want to have to empty out his flush machine and fill it with Honda fluid…I don’t blame him. Honda’s have VERY tender transmissions and if using “special” fluid somehow keeps them alive, so be it…


#15

I had to gin up a filler using a motor oil filler and some Tygon tubing. Fortunately, I had the tubing in my garage already. It took a while to find the right oil filler, though. I suppose you culd use a funnel, but it would have to be awfully narro to fit into the dip stick tube. I never found one I liked.


#16

Does your manual say to drain and refill it one time or three times? What did the mechanic do? If it’s three times, that gets enough of the old fluid out.


#17

I agree with Honda…when trying to change my trans fluid I just pull the trans drain plug during an engine oil change and get the 3 or so qts out at that time and refill…then I repeat this for the next 3 or so oil changes. That get it all out and replaced with fresh fluid and avoids the dangerous full trans drain that seems to wreck some trannys. This method has been working without issue for me for over 15yrs.


#18

That sounds like a good plan. But some more of the Honda fluid and just plan on changing it ~3X as often as I had in order to largely replace the existing fluid and make note of the volume coming out to make recharging easier. Thank you!