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Transmission issues with my high mileage 03 Sonata

4 cylinder Sonata with 177k miles on it. When I first get in the car and drive away the transmission doesn’t want to shift up. I have a manu matic type shifter so I usually just shift up as the RPMS reach the normal shift point. Eventually the transmission starts working but sometimes it acts up and I’m back to shifting myself. Sometimes it shifts hard or double shifts. I’m getting conflicting info from different mechanics. Some say change the transmission fluid and that should fix it. Others say don’t because it could open up a bigger can of worms and I will be buying a new transmission shortly after. What should I do?? I can’t afford a new car nor can I afford to buy a new transmission. HELP!!!

Did you at least check the fluid level in the trans ?

This sounds to me like a transmission that has not been serviced as it should have been.

Have you changed the fluid every 3 years/30k miles?
If not, you are very likely to be in the situation of having to pay for a transmission overhaul in the very near future.

If I were you, I would do a trans fluid change (including filter, if so equipped), and then repeat it in ~1,000 miles. This “Hail Mary Pass” may give you a few thousand more miles from the trans, but then again, it might not. It is truly a gamble. Transmissions that are not serviced on the schedule noted above are prone to failure any time after ~90k miles, and failure is essentially a sure thing after you pass ~120k miles.

This trans should have been serviced 5 or 6 times so far.
What is the maintenance record for your transmission?