Hyundai AT does not like overfill

[kgb007stb]

I found out that at least my Sonata 2.4L AT doe not like to be overfilled. In an effort to evacuate all the old fluid out through the cooler line, I mistakenly overfilled the transmission by about ¾ quart where the level of fluid was showing well above the full warm level mark. I was not very pleased with the shifting over the next two weeks of driving, took that as a signal that some fluid would have to be extracted. Upon extracting ¾ qt of oil, level dropped back to the ½ mark on the warm mark after full warm up, unlike the previous shifts, shifting resumed back to the normal crisp shifts as expected.

Did anyone else experiment with the Sonata AT fluid levels which yielded the best shifting results?

 

[deeter16317]

I found our subaru trans doesn't like overriding either. But I was almost a full quart by mistake...the dipstick is hard to read after you slop fluid down the tube.

 

[4x4chevydude]

Ya its almost impossible sometimes to tell how much you got, thats why i play it safe and do research about how many qts it should have before i put them in I would imagine most cars dont like to be overfilled with ATF but my sonata shifts funny and its at the full mark so I think Hyundai transmissions may shift weird.

 

[wymi516]

I definitely agree, my 2009 Santa Fe 3.3L is very sensitive to overfilling the trans oil. I usually try to get the level between the two notches on the 75c side with the trans hot. What a pain it is to do that, the dipstick curves to the right and then goes down. I don't get why there's a "cold" 25c mark on the dipstick either, It always reads high when I check the trans cold.

 

[Rand]

I usually check dipstick.. measure fluid removed..
put that much fluid back in -.25qt

top up a day or 2 later when its convenient and I can read the dipstick(and trans warmed up)

I did have my hyundai elantra touring about .25qt over due to brain failure while adding up what I got out.
that was ok as I was doing another drain and fill next day.

 

[wymi516]

Can anyone here shed any light why there is a "cold" mark and what it means?

 

[doitmyself]

Originally Posted By: wymi516
Can anyone here shed any light why there is a "cold" mark and what it means?


For this Hyundai in particular, or all cars in general?

In general, transmission fluid "expands and contracts" a LOT with temperature changes. The cold marks are to measure the fluid level at "cool" (sitting overnight) conditions. To measure more accurate, it is better (my opinion) to get the vehicle up to operating temps. (thermostat functioning) and measure the "expanded" fluid between the "hot" marks.

This expansion/contraction can make dipstick readings kind of funky. I usually get my fluid to be a bit underfilled while hot, then over the next few days measure and adjust the level up a bit. If you filled a cold tranny up to the full hot mark, the fluid would expand when heated to become overfilled.

 

[wymi516]

Originally Posted By: doitmyself
Originally Posted By: wymi516
Can anyone here shed any light why there is a "cold" mark and what it means?


For this Hyundai in particular, or all cars in general?

In general, transmission fluid "expands and contracts" a LOT with temperature changes. The cold marks are to measure the fluid level at "cool" (sitting overnight) conditions. To measure more accurate, it is better (my opinion) to get the vehicle up to operating temps. (thermostat functioning) and measure the "expanded" fluid between the "hot" marks.

This expansion/contraction can make dipstick readings kind of funky. I usually get my fluid to be a bit underfilled while hot, then over the next few days measure and adjust the level up a bit. If you filled a cold tranny up to the full hot mark, the fluid would expand when heated to become overfilled.

What gets me is, if I check the trans oil cold, first thing in the morning. That's when on both our Hyundai's, 2007 Sonata I4 and my 2009 Santa Fe the levels read high past the full hot mark. After reaching operating temp and driving the cars long enough to get the trans oil hot the levels read perfect. Why can't the mfg's just figure out where the right level is on the dipstick when the trans oil is cold, like motor oil. I understand the level changes when hot.

 

[4x4chevydude]

I agree with the above but not just Hyundais its any trans ive ever serviced