After last transmission service I noticed that transmission fluid is about 1/4" above the maximum mark. Does anybody know whether it's good or bad or doesn't matter?

 

overfill = bad

drain some out.

 

As far as I know, overfilling an automatic is harmless. When it gets hot, it just blows the excess out the vent.

Don’t confuse this with overfilling an engine. The crankshaft will whip up the oil into a foam and reduce lubricity of the oil.

If someone disagrees with me, please explain WHY.

 

same reason its bad for the engine.
what do you think the output shaft and gears will do when theyre sitting in atf. bands and clutches are very sensitive to foaming

better to underfiill than overfill

 

are you really sure it's overfilled? If the car is not level and you haven't run through the gears first, then you're probably not reading it right.

if it really is overfilled, go back to the place you got the service done and have them drain it. I don't think tranny fluid has as many detergents as oil to whip up into foam, but there's a max level for a reason so don't go past it.

 

Are you checking with the engine warm and the engine off? Most other cars that I've dealt with are done with the engine running and as Medic says run through the gears. On the Honda/Acura, the tranny is checked the same way as the engine oil. Engine off, warmed up, and on a level surface. If it's still over filled, I would drain some off (or suck some out through the fill hole).

Hope this helps.

 

Acura dealer fills mine and mine is over the full mark too.

 

Thank you all guys to reply! Answering some of your questions whether I am sure it's overfilled and how do I know that. I just followed the manual - parked on the horizontal portion of my driveway, let it sat with the engine off for about 5 minutes and checked the level.

 

Maybe on Mars overfilling a tranny is OK - foaming is also an issue in an automatic, or any transmission for that matter. as you said, aerated lubricant is essentially no lubricant.

But 1/4" over is unlikely to harm anything.

 

This happened to me once, Acura over filled it, and I noticed the tranny slipping, so I took it back to them a few days later and had them re-do the tranny service. I havn't had a problem since and that was 6-7 monthes ago. Now, I havn't had my car for 48 days now, since its gettin repaired (or not getting repaired) at this stupid body shop in the middle of east Jesus Alabama, so I dont know if its going to run right or not!

 

YES, IT DOES MATTER. Two times now when overfilled several oz. my '03 CL-S lockup clutch cycled off/on (noticeable on tach) especially before warmed up. When brought down to proper level this abruptly quits. No telling WHY but that's a fact, & no telling what other issues overfilling causes.

It's important to understand the upper/lower dipstick marks are for when it's at operating temp, & that as it cools down a large amt of fluid drops into the sump. So when cold, it is ok if slightly above the upper mark but no more than 1/16 - 1/8"
or yes you could be overfilled. I've found this out the hard way! To not overfill is a pretty specific balancing act, & your best bet is cold just ensure you don't exceed the very upper mark. That way, warmed up your level is about 3/4 on dipstick & all is good. Of course if you want absolute full you can add to it while warm to upper mark, just understand there's no benefit to that so why do it then? Of course it goes without saying it's vital this all be done on level ground!