NOT SURE OF WHAT RADIO YOU HAVE BUT A Y HARNESS IS YOUR BEST BET A SLOW SERVO MIGHT BE BECOUSE OF A WEAK BATTERY SHOULD RUN A 6 VOLT BATTERY ON ANY HIGH PERFORMANCE PLANE OR REVERSE ONE SERVO IN THE PLANE HAVE RUN MANY DUAL SERVOS ON ELVATORS , COULD BE A BAD SERVO // CHANGE IT OUT FOR ANOTHER ONE AND TRY AGIAN GOOD LUCK