2001 Sonata V6, auto tranny. Bought as a program car with 16K.
Currently has 50k on the odometer. As I had driven a manual tranny for
the past 20 years, little things I noticed about the shifting of the
AT was dismissed as not being used to the typical occasional hunting
such trannys do. Basically would note when accelerating that the
tranny would shift early, not winding out to take advantage of full
torque.

As an aside, noticed that the front brake rotors were slightly warped
and would be needing turning soon. Noticed gas mileage dropping. Came
up on a stretch of highway with traffic lights on each block. Engine
would rev to 4000~5000rpm quickly and AT would dump to next higher
gear. In high gear doing a max of 30mph or so and struggling to
maintain speed. Felt like water in gas. Vehicle would eventually speed
up to maybe 45mph. Stopp and several minutes later the vehicle would
run okay or 98%. After several attempts by the Hyundai service
department, they finally claimed it was due to all four brake rotors
being warped badly to the point they couldn't be turned. (It
apparently was so bad that when it occurred, the vehicle would not
roll forward while in DRIVE and no foot on the gas pedal) They even
said the brake system needed to be flushed as the fluid had even
"boiled". I had the rotors replaced, pads replaced, the brake system
flushed and even the AT fluid flushed, serviced and changed. Due to
work restrictions, vehicle stayed at shop an additional 2 days, upon
arriving to pick up, found that the service dept had decided to
replaced the brake master cylinder as they were concerened it may have
problems in the future. They had indicated that the brake fluid
smelled "funny" and didn't seem like brake fluid so that was also a
concern. This replacement was handled under warranty. 500~600 miles
later, problem returned. In speaking with service dept they indicated
the tranny probably was acting up due to the strain it had been under
prior so they would handle it as a warranty issue. I have yet to be
able to get it to the shop however I have noticed the brake rotors are
warped again (less than 700 total miles) and the brake pedal is ROCK
HARD with no travel downward or upward when the situation occurs. It
has been discussed that this actually may be a brake booster problem.

Has anyone encountered such a problem with their Sonata? If so, was it
a brake booster? Thanks in advance!

What'sup!