Originally Posted by LasagnaCat

Did you move the servo horn along with the servo, or move the servo and try to reuse the horn on the first vehicle? I'm not familiar with those brands, not sure how many teeth each one require for the horn... someone else will probably chime in with that. Always start with the obvious, horns are not always interchangeable. If you did move the servo horn with the servo as it sounds, you may have just stripped a gear inside the servo.. that's the other most obvious thing to check.