She’s my car has difficulty in an automatic transmission going into gear past 40
Okay, if I’m interpreting your post correctly, either your transmission doesn’t shift when the car reaches 40mph or it feels like the car drops out of gear. If your transmission has a dipstick, start by checking the transmission fluid. Make sure it’s at the correct level and isn’t excessively dark or burnt smelling. How many miles are on your Sonata and when was the transmission fluid changed last?
Your car has a 4 speed transmission so if you feel three shifts that’s all you’re going to get. It’s possible the torque converter lockup isn’t working, which can make it feel like the car isn’t shifting that last time. If that’s the case it will be much cheaper than a replacement transmission. But the only way to know is to take it to a good independent transmission shop.
Take it to a transmission shop and have it looked at . The car is 16 years old and things eventually fail . Then you have to decide if it is worth the cost of replacing the transmission at multiple thousands of dollars or not if it comes down to that .
No argument but it would be nice to find out what’s wrong first and get an estimate, no? A 15+ year old vehicle might well be worth a new torque converter solenoid, if it’s in good shape otherwise