Ford F-250

I have a Super Duty F-250, 4WD, 170,000 miles, 7.3 Diesel, and recently it has been acting funny. Occasionaly when I stop at a red light, the speedometer needle begins to jump and climb in speed reading while the Engine RPM begins to idle irradically almost shutting off, but when I put the transmission on park and let off the brake it goes back to normal idle and the speedometer goes back to zero. What could this be? I have previously installed a TruSpeed control box to adjust my odometer due to my oversized tires, and had to disconnect the cable assembly into the ABS system, could that have anything to do with it? I also ran a diagnostic test using an OBD II compliant scanner that gave me an error code of P0722 and P0720 (Output Shaft Speed Sensor Circuit [No Signal]), but I'm not sure what that means. Can you help me?
July 23, 2007.

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