Having trans problems on 2010 elantra
 

Well im new to site, a little background about myself im retired Marine, motor pool mechanic, so im not dumb, just new to Hyundai's, well heres the issues, have drained and filled using factory fluid, it first started with 2nd to 3third shifts being very hard, now if i run it around town and get trans warm, it falls in and out of gear, have read code with my scanner and get a 700, and 734, and i guess my final ? is does this sound like output senser or do i need to rebuild trans? all input would would be great.....