My 2003 Dodge Grand Caravan is throwing the codes of P0700, P0720, P0731, and P1176. The speedometer bounces while in idle and lately has locked up in "limp mode". I replaced the output sensor and the problem seemed better (needle wasn't bouncing as bad) but after a few days it becomes worse again. Any thoughts? Perhaps the Transmission Solenoid pack gasket clogged?

 

Think you would want to check the wiring and connector of the input speed sensor before doing anything else, and then if it looks ok, try a new one of those. Yes there are other possible suspects, but the P0731 points directly to the input sensor.