Purchased new 2018 Sonata sel model in California. While driving, the transmission starts to hard downshift when the brake is applied. I found out that this hard downshifting and jolting/thumping of engine and transmission only occurs when coming to a stop at speeds between 10 to 15mph. It can be described as follows, after the brake pedal has been gently applied and lightly released but then the car itself applied its brake again. It terrifies the driver's driving conditions, mentally and physically.

- Los Angeles, CA, USA

Throttle response: Feels like the old vehicles with a flat spot in the carburetor accelerator pump. The "three second' rule applies when the throttle petal is pushed. There is a serious hesitation as the engine tends to fall flat before accelerating. Has to due with the six speed automatic transmissions duel clutch which acts as if a person were operating a standard transmission clutch. I have discussed this problem/concern several times with the service department where the vehicle was purchased. The service department indicated they receive numerous complaints. It is indicated the drivers either love the vehicle with this problem or hate. We were never told of this situation. And there is no fix for this. This situation can occur when leaving a stopped position, when turning right or left from a stopped position, accelerating up a hill in moving traffic or on a street. This all depends on the drivers reaction to the throttle pedal. When one needs to accelerate while in motion there tends to be a shuddering/stuttering of the engine. This problem has occurred shortly we purchased the vehicle in February 2018 and has been on going. I set the "when did this happen" as starting date. Can be vary concerning when entering traffic for older drivers. I cannot find any more descriptions for this situation. There are no documents at my disposal at this time. Thank you.

- Auburn, WA, USA