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Transmission intermittent very hard shift downshifting

4.4K views 4 replies 3 participants last post by  eagle.h123  
#1 ·
Hi all,
I have a 2015 Sonata SE 2.4L with 148,000 miles. At about 140,000 miles I was driving back from the store and as I was coming to the first stop I felt a hard bump when the car downshifted, either from 3rd to 2nd, or 2nd to 1st. It was startling to be honest, as if I ran over a deep pot hole. I pulled into another parking lot and turned it off, then turned it back on, and it stopped. Didn't do it again for another few thousand miles, and again i turned off the car and back on and it stops. So far it's done it a total of 4 times in the last 8000 miles. A little background, i was unfortunately dooped by the "sealed transmission" advertisement and never had a transmission oil change done. I already did 1 drain and fill, but that was after the second time it bumped. I am going to do 2 or 3 more to get most of the fluid changed, however i'm thinking of pulling the solenoids, testing and cleaning them up to rule out that issue as well (and some cleaned up solenoids wouldn't hurt). I found this guys video on doing this to his Kia, which i was going to try:

If any of you think i may be going down the wrong road, please let me know if there is something else i should be doing before this or instead of this.

If not, then my main question has to do with removing the transmission pan cover over the solenoids. After getting the cover off, this type of work is no problem for me. However there is a transmission oil cooler mounted to the front of the pan cover. It looks like it is just mounted to the pan cover, and not feeding fluid in through the cover. Does anyone know if this can be moved back to be able to remove the pan cover, or is it going to have to be removed?

I couldn't find anyone who's tackled this before online on a Hyundai. Any help is appreciated.

Thank you!
 
Discussion starter · #4 ·
Glad you found the culprit before serious damage was done.

For grins, you may want to stop by an AutoZone or O'Reilly's auto parts store. Many have sophisticated OBD II scanners that they will check your car for free. The bad solenoid undoubtedly generated a code. Good to see what else may be going on.
Thanks! I did actually do that at AutoZone before starting the work and there were no codes.