2009 Hyundai Sonata Q&A
2009 Hyundai Sonata Question: auto transmission shifts hard
You should still be under warranty, I suggest having the Hyundai dealer look at this to see if there are any diagnostic trouble codes stored, Technical Service Bulletins related to this issue or software updates for the transmission control module. Here's some near you: http://repairpal.com/directory?address=72949&car_brand_names=Hyundai - Bret Bodas
When car is 1st started on cold days (approximately 40 degress and below) the trans kicks hard when car speed is decellerating. After engine warms up, the problem goes away.