Hyundai Repair: 1999 hyundai sonata, hyundai sonata, range switch

Question
i'm having a similar problem. sometimes when you take off it will rpm really high then bang into 2nd gear, same as thrid. but won't shift into high gear and if i stop and take off again it hardly has any power and still shifts hard. if i shut it off sometimes after 5 mins or up to a hour then it seems to be ok till the next time it happens. i'm getting code #'s P0715 & P0705. any suggestions?

Answer
P0705 indicates a malfunction with the transmission range switch.  It is usually corrected by replacing the range switch.  Before doing this, though, recheck and verify that you are indeed getting code P0705.  It's not clear that this code is even used by the 1999 Sonata.  If you mistyped or misread the code, please follow up with the actual trouble code.

P0715 indicates a problem with the input speed sensor signal.  I have never seen this code occur other than a problem with the sensor itself.  Replacing the input speed sensor will almost certainly remedy this code.

The input speed sensor is also consistent with the symptoms you describe.  Presuming the trouble codes you report are correct, replacing the input speed sensor and range switch will likely resolve all your issues.