My 350 with a 4l60e runs perfect up to 45-50mph. Once it hits this speed it just cuts out until the speed is lowered back to 45 then is fine again. The only code it threw was a code 83. I don't know how this code would make it shut off over 45mph. Any help is greatly appreciated. The wiring harness was made for this combination but I wouldn't rule it out i just don't know anyreason it would make it to this speed everytime then cut out. It happens every time without fail.