Hobby servo problems

we are using the vex cortex and controller to control a robot for the skills ontario challenge. This is a bot made of machined and welded components so we dont really use vex components aside from the controller. We are trying to use a big servo for an appication on the bot. We use easy c and we cannot get the servo working well. It seems like the servo reaches its end travel capacity on one side of its travel. I tries setting the limits to 35 and -35 to reduce the travel but it dosent seem to stop the funny sounds. is there somethings i should know when using r/c servos?