when you blow a gear set...your main gear (what you bolt your servo horn onto) is what controls the way the motor spins.....center it...and the motor's will stop zzzzzzing....turn it left the motor turns gears (or should) If the gears are stripped...but if they aren't...i dont see anything that would prevent the servo from working normally....Stuff like this is Sooo much easier in person to diagnose.
FYI opening a servo does NOT void the warranty.