If your in the right forum then your fuel shut off solenoid rod is not dropping when your turn the key to off. (Engine not shutting down. )
The engine speed sensor located on top left side of damper could be unplugged,miss adjusted or bad. ( The engine speed sensor runs the tach, lets the pcm know the engine is running so it will tell the alternator to charge and occasionally keep the speedo from not working for some strange reason. ) the connector to the vehicle speed sensor could be unplugged or bad.
But take it back to trans shop to see what they unplugged.