I have a 2003 Sorento that I have now taken to a transmission specialist and he cant seem to figure out what is wrong. First of all it wont shift into overdrive, 4th gear etc. gears 1 2 and 3 are fine. It shows that by the indicator light that it is stuck in 4x4 but it is not. The mechanic said he hooked it up to his machines and the communication failed twice. The tran fluid is dark. He said it might possibly be the overdrive has burnt out or something more than that but recommended taking it to a dealer. I previously took it to a local regular mechanic (doesnt specialize in transmission) and he got the same results with his diagnostics. I really hate going to a dealer cause Im sure they will new "needs new transmission". I am really stumped at the fact that a transmission specialist could not figure out what is wrong with this vehicle. Any immediate help would be deeply appreciated. thanks it has around 180,000 k miles on it.