I bought a 2017 Hyundai Elantra brand new at a dealership in 2017 (it had 4000 miles on it but they weren’t from a previous owner, maybe transport miles?). Anyway, I have done all maintenance early or on time, and drive it like a grandma. About 2.5 years and 30K miles, the transmission started shifting rough. Not a jerk or kick really, just not a smooth shift.

Around this time I found a bunch of water behind my dash because of what I found out later was a clogged AC drain line. I put my wet vac on the tube under the car for a sec and watched water gush out. I dried behind the glovebox area and noticed the transmission shifted a little smoother but still a noticeably rough shift.

The hard shift also started around the time I used the “shiftronic” (manual mode) shifting, as I was going up steel hills frequently at the time. So I’m not sure if that had anything to do with the shifting issue, or whether all that water damaged a sensor somewhere which is maybe causing an electrical issue not a mechanical one??

Being under warranty I took it to the dealership and they said they also aren’t getting any codes, so they reset the adaptive learning, which did nothing. Then I had them change the fluid. I noticed a slight improvement but it was still shifting rough.

Fluid level was checked and is good, and the dealership said they can’t duplicate the hard shift, so I dropped it off overnight and they drive it in the AM (30° out) and claimed they couldn’t feel the hard shift (which is IMPOSSIBLE).  They’re giving me the run around, said “don’t worry about it until the check engine light comes on, then bring it in”. Hell no!  Each hard shift is causing damage little by little!  Please help!