Got a 2013 Hyundai Sonata limited, car stalls when you put it in drive or reverse. Engine runs fine, but soon as you put the car in drive, it stalls. Dealer is telling me the torque converter has locked up and the whole transmission needs to be replaced. I am trying to do the research but does the whole transmission have to be replaced when this happens? I have a 2011 Hyundai Elantra, that we had a problem with the Torque converter that went bad, didn't lock up, but was under warranty back then, so they replaced the whole transmission since they said it was easier to just replace the transmission instead of replacing the torque converter, but my Sonata is not under warranty anymore. So trying to get some advice from anyone if they know anything about this kind of issue.
By the sounds of it, a locked up torque converter sounds accurate.
There are some things to keep in mind.
Most torque converters have a built in "Lock Up" functionality to improve mileage when cruising as it prevents losses due to the fluid coupling.
I would expect either just the torque converter needs replacing (although there are not many moving parts in torque converters so not a lot to fail), or the Electronic Solenoid that controls the Lock-Up motion needs to be replaced as it may be stuck activated, it would be unlikely that the entire transmission needs replacing.
Since the transmission still shifts in to gear (it stalls the engine which means the gears are engaging fine), I would be extremely hesitant to replace the whole transmission. I would get multiple quotes from multiple mechanic shops and see if they all agree.