My 07 commander 4.7 shifts irraticaly on hyway going about 65 70 mph. It downshifts then upshift and repeats irratically. The fluid is full, clean and doesnt smell burnt. What will caise this...shift solenoid or controller or valve or something maybe. I am a certified diesel tech and can do the work myself if i knew wtf to change. No cel or any other light on dash ever display.