Transmission trouble
 

My 2004 Sonata with the 2.4L 4cyl with an automatic in it is slipping a little bit when it shifts. It's got 105,000 miles on it. Is this normal at this mileage? How expensive is it to have them rebuilt? Can I get a trans out of a junk yard? Does my trans have a model number that I should look for before buying a used one? If so, what models and year ranges would have the same transmission in it.

Have you ever changed the trans fluid?

No I haven't. Do you think that would make a difference?

Not changing the fluid is the leading cause of auto trans failure. Sounds like the valve bodies are sticking from dirty, gunked up fluid. You're supposed to change the fluid every 30k miles.

Yep, like jsinton said, change it every 30K. It's probably too late now (I hope not) but try flushing the trans first.

I wouldn't say it's too late just yet. Changing the fluid in a situation like this can work like magic. It still shifts, so I would guess just changing the fluid would make a big difference.