2001 Ram 1500 4x4 Sport code P0720

I have 2001 Ram 1500 4x4, with 5.9 V8. The computer has been tuned to a rev limit of 500 rpm. The tire size of 35 inches has also been downloaded. The engine has headers, throttle body spacer and Airaid air management system. It has been runing fine up until today when the oil pressure gauge elevated to 110 while under load. When the vehicle is not under load it returns to 60. It also will hold proper pressure in park and can be reved without change. The transmission will disengauge and engine will rev. under excelaration. The code P0720 came on and I was told that it was the speed sensor on the passinger side of the transmission so I changed it, but I am having the same problem. I did find out that the sensor which I changed was the input speed sensor and the code was a output speed malfuntion. Can anyone please advise me on my next step? Would the output speed sensor cause the problems that are occurring and were is the output speed sensor on this pickup? Thanks, Les

The transmission output speed sensor is located in the overdrive gear case. The sensor is positioned over the park gear and monitors transmission output shaft rotating speed.