Prior to replacing the automatic transmission fluid (to improve shift quality), make sure that the transmission fluid level is correct. Also, make sure the computer that controls the transmission has the most up-to-date adaptive programming information. When servicing these transmissions be sure to use fluid approved by Hyundai.
Car Problem Reports
Hyundai Sonata Confirm Latest Software For Transmission Control Module and Correct Fuild For Proper Shift Quailty
Hyundai Sonata Problem
Drive Train Affected: Automatic Transmission
Average Mileage: 50,601 mi (10,000 mi - 96,000 mi)
Visitor, 2010 Hyundai Sonata, Automatic Transmission, 65,000 mi
I noticed that my car is beginning to down shift with a hard thump at 20mph. Has anyone had this problem?
Visitor, 2009 Hyundai Sonata, Automatic Transmission, 71,000 mi
Hard violent downshifts when drive car while cold. Almost disappears after warmed up. Harder upshift when cold. Will be taking to a dealer to diagnos issue.
Visitor, 2010 Hyundai Sonata, Automatic Transmission
HARD down-shift always between 20 - 25 mph.
Visitor, 2009 Hyundai Sonata, Automatic Transmission, 96,000 mi
not fixed, I shift into neutral, when coming up to stop signs--Jerky downshift -- if I don't put it in neutral.
At times,before reaching normal operating temp.transmission would shift into next gear with a very very hard jerk.This would not happen all the time.Thank you
Visitor, 2009 Hyundai Sonata, Automatic Transmission, 20,000 mi
hard shifting when car decelerates down to 20 mph feels like a shift from 3rd gear to first; Throws you out of the drivers seat into the brake pedals; another problem was in Washington D.C. when the car accelerated by itself, just like the Toyotas, in the parking garage of Arlington Cemetery and almost hit parking cement post. The Cemetery guard hid behind the post and unsnapped his holster when I finally got the car stopped. Both feet on the brakes and it kept going . I was really scared. But the first problem Hyundai ran from it and said " I had been burning out with the car " Can you imagine an unpowered four cyclinder front wheel drive doing anything like that; HYUNDAI get off the sake . Hyundai said " I was the only one having the problem , wrong again , check Edmunds.com and You Tube the world is having problems with transaxles. Change the fluid everytime it starts bumping but that like 3000 miles ; The other problem isn't fixed and I am afraid to drive the car. But to lie to the customer and say no one else is having problems BULLSHIFT . Software must be changed to get this to run right . I wish I could find the transmission modual and unplug it and reset it by default ill bet that would work. Okay when the car was new It sprayed a fliud all over the underhood and soaked the serpentine belt and corrupted the belt . Okay I like in Charlotte at the time I was in Clearwater , FL Hyundai tells me to drive it back to the Charlotte dealer with the belt melting away as I called them. They never determined what that was never I don't know to today. But no hotel free or tow truck to tow it back home or rental car like they promised , Nothing goose egg. They are PHONIES and should be arrested by the department of Justice for Auto Terrorism. they still haven't fixed my tranaxle and refuse to program it why me because Im not KOREAN why GOD WHY DO people do this in the U.S. James Lee replace and refresh the transmission fluid helps make it go away after the empty of fluid only 4 quarts or less, replenish with diamond fluid from HYUNDAI okay then drive the car on the freeway to reprogram by default it will start clearing up after five starts and drives. That's how it works it senses your driving pattern Okay.
Visitor, 2009 Hyundai Sonata, Automatic Transmission, 65,000 mi
Each morning when coming to a stop harsh down shift into 1st gear, but will go away after warmed up. Took into dealership and they did update to ECM, which was not covered under warranty, so much for the 10yr 100,000 mi warranty.
Hard 2-1 downshift when the weather got near freezing and the car was cold. Reflash of the computer programming fixed it for awhile. It came back and another reflash and trans fluid change fixed it for good. The trans fluid had been changed 20K earlier but the dealer noted some discoloration so we changed it again. Didn't want to mess around with a more exopensive problem later.
Visitor, 2010 Hyundai Sonata, Automatic Transmission, 43,000 mi
The transmission is hard downshifting into low gear when transmission is cold, quits when running warmed up.
Visitor, 2009 Hyundai Sonata, Automatic Transmission, 55,000 mi
Had hard downshift issue around 55k. After a couple of reflashes the ended up putting in a trans. Said the old one wouldn't take the latest update. Now same issue at 120k and the warranty on the new trans expired at 60k with everything else. Haven't taken it in again yet.