97 audi a8 tranny problem g38
 

Hi guys ,
I replace the transmission on my 97 audi a8 3.7 ( used one)and I was driving it on the highway everything was fine untill I felt something like the engine was missing for a second and then again after 30 seconds .I took the exit to put some gas I shut off the engine and when I stared the car there were no gears the car was not movin at all. after u rev the engin to about 4000 rmp the gear indicator lits ( limp mode I guess)
transsmision code 00297 -gear box speed sensor no signal g38

also I had some ecu codes 18010 power supplyterm 30 volt too low,18014 rough road/engine torque signal electrical malfunction,16515,18032, 00302 abs selenoid valve relay and p0300 random misfire.
Where shoud I start ? Is it possible to have a bad torque converter ( i didnt rebuild it) .?how do I test it? Or shoud I just replace the speed sensor g38?