About 5k ago my VQ 05 frontier (156k) started to make what sounded like the dreaded timing chain guide whine. Lately it sounded like it was getting a bit louder. I was just about to order the parts to do the replacement and the noise just went away. Is this a sign that something catastrophic is going to happen or could i have been a misdiagnoses? What else could make the wirrring sound and then silence?