Yessir. What I'm guessing happened is within the last 300 miles you were rough on the engine braking/downhill descents. This wears the inner portion of the belt significantly which makes the ID of the belt a larger diameter. All while wearing the outter portion of the belt slightly. I may be wrong though. Just a thought. I've seen this happen a lot! The inner part of the belt that rides on the bearing gets worn down quite a bit. People often over look this.got it....I would bet you a cold one that if/when you install a new belt, you will be using 2 spacers in the secondary to start with......