Hyundai Repair: trasmisson, fine cars, output speed

Question
was driving yesterday when car didn't, want to change to second in my sonata 00 model then when it did it jerked real bad and has done it since , other gears fine cars starts and runs normal any help would be great

Answer
This could be an issue with an input or output speed sensor, or it could be a serious issue inside the transmission.  

If I were able to look at this vehicle, I'd want to do two things:
-- check for diagnostic trouble codes
-- if none, monitor the input and output speed sensor with a scan tool and check their readings.

You may be able to accomplish checking for trouble codes yourself by taking the car to AutoZone or similar place that will read the codes, but you'll probably need to take it to a qualified shop to do further diagnosis if necessary.  I recommend the dealer for transmission issues simply because transmission repair chains tend to approach every car as if it needs a transmission.