Do you have a good scanner? There might be codes, but with no lights on the dash. Its kind of common to have transmission codes and no lights on the dash. The dash lights usually only light up with stuff that can cause emission issues. I would say a solenoid in the valve body is bad or sticking not causing it to shift.
2008 3.0L CRD WK LTD - Wifes, GDE DPF Delete Tune, Turbo Resonator Delete, 3" Intercooler, Kolak Addcoo Front and Rear Sway Bars, coming soon 3.07 gears & SRT8 Wheels
2007 3.0L CRD WK LTD - Mine, Custom Spooling Tune - Stage 2 Performance DPF & EGR Delete, Custom Cold Air Intake , 3" Intercooler, Turbo Resonator Delete, DPF Delete Pipe, Devil's Own Methanol Injection, SM resistor plug, SRT8 rear springs, SRT8 rear sway bar; 255/70/17 Hankook ATM's, dechromed stock wheels
2003 F250 6.0L CCLB - Gearhead Tunes