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: 58,160 mi (10,000 mi - 145,374 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, 2011 Hyundai Sonata
Sonata Limited.I've had transmission problems starting at about 6 mos. and several times since...ECM & hard shifts, like someone hit me! The ECM should be covered by warranty. Poor gas mileage since about same time but ironically, this specific yr/model excluded from the class-action lawsuit that was awarded. Too many other problems to list. I'm afraid to take on trips, too. What a lemon! I'd never buy another one! Shame cuz a beautiful car...but looks don't make it run and get me where I need to go. Going back to Toyota!
Visitor, 2009 Hyundai Sonata, Automatic Transmission, 80,000 mi
Last year my Sonata started downshifting when driving on the freeway, on its own. I paid over $100 to get the dealer to fix it. They said it was a software glitch and they fixed it by loading new software. That was 2013. Now (2014) it downshifts hard when I'm braking in city traffic. If I'm going to have to pay this every year, I may be done with Hyundai. Other than this problem, it's been a great car. Hyundai needs to take ownership for this defect.
Visitor, 2010 Hyundai Sonata, Automatic Transmission
HARD down-shift always between 20 - 25 mph.
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.
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, 60,000 mi
Hard downshift from second to first when cold.
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.
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.
Problem of hard downshifting when cold encountered almost every year since car was new. Reprogramming adaptive values is the approach dealer took every time, and the problem would go away for nine months to a year. After the warranty period was over the car started doing it again and reprogramming the values did not solve the problem. Hyundai did honor extended powertrain warranty and ended up replacing the transmission, which--believe it or not--did not solve the problem! Two more reprogrammings later finally did the trick. Now I'm waiting to see what happens over the next few months.