P0700 is a generic transmission fault code, it only means that the PCM sees that the TCM has set a fault code. The only way to not waste money on unnecessary parts is to have the TCM scanned.
You could do a quick check on the speed sensors with a simple multi meter. Both sensors are the same and should have more or less the same resistance. An open circuit means a failed sensor. Best is to remove the sensors, because it is not that easy to measure in place. Just remove the connector and one 8 mm bolt and you can simply pull them out.
Speed sensors fail quite often on these transmissions, TCM not.
JEEP Grand Cherokee 4.7 Lmtd 2004
HID 8000K in low and fog / Quad Squad member
KYB Gas-a-Just shocks / Pirelli Scorpion ATR 245/65/17 - Transgo reprogramming shiftkit.