Trans wont shift reverse,Forward lags until warm. Code 700&731 Otherwise PERFECT

Code 700 refers to a diagnostic code stored in the Transmission Control Module (TCM) Code 0731 refers to a gear ratio error in 1st gear. This code is set if the gear/speed ratio is not correct for a period of time. It may be as simple a an Input or Output Speed Sensor, which is relatively inexpensive to replace, corroded or loose wiring connectors and worse case, slippage within the transmission. I would replace the output speed sensor first.