First my ABS light came on,then my brake light,then my speedometer stopped working finally my check engine light came on.This was all during a 20 minute ride home.I pulled the rear wheel speed sensor in the rear diff and only the inside of the part came out.The sensor had broken into 2 pieces in it's position.Went to the dodge dealer,got the sensor.Problem solved and it only took $37 and about 15 minutes worth of investigating,removing and installing.

 

yea same thing happened with my dad's 3.9. first it would only shift at the WOT shift points no matter how lightly your foot is on the gas, then it just stopped shifting. so i changed the diff. speed sensor and it was cured.