Overfilled Tranny with ATF, should I be worried?


#1

How much tolerance do you think modern automatic-transmissions have for underfilling and overfilling?





Why do I ask? Well, after doing a drain/refill, I may have underfilled it by .25Quarts and upon finding this out, I think I overfilled it by .25 quarts… heheeh



It seems with trannys, there is much less tolerance than Engine oil.



And measuring the amount can be a pain in the butt, amirite??



You have to satisfy certain conditions such as hotness or whatever.



Car: 2007 Corolla Ce


#2

I would not worry about the 1/4 qt. I have run transmissions over the years slightly overfilled and had no issues. It can be a painful process to hit the mark on some transmissions. Note that an underfill by .25 qt should have been in the OK range and you would have been well served by leaving well enough alone.

If I have a drain plug, I would consider draining a slight amount, but I had to remove the pan, I would leave things well enough alone.


#3

How long was the vehicle driven with the low and overfilled fluid? If they were short periods, I wouldn’t worry about it.

Having done this job before, I know what a pain it can be. The last time I did this type of job, I overfilled it. Then I drained enough out that it was a little low. Then I would add fluid, drive it around the block, check the fluid level, and repeat until the fluid was at the right level. The way I see it, at least you and I managed to change more fluid than we would have with a normal ATF drain and refill.


#4

If this is one of those cars without a dipstick, then the following will not be helpful at all:

Check it a bunch of times in the near future, especially when it is good and hot - so after fairly substantial drives. If the fluid looks all foamy when you check it, that would be bad.

Either for that reason or for peace of mind if it matters, you can easily pull some fluid out of the dipstick tube. Use any piece of clear tubing that fits - I’ve done this before with my mouth (obviously not the most preferred method but its fine if you’re careful) and by small hand pump.