Just a couple weeks ago I was rolling down the highway when my CCT spring broke and it sounded kinda like that. Sounded like all hell broke loose in the right side of the motor. F'N LOUD repetetive noise affected by rpm, not chaotic like something fell off in there. With mine the sound went away if I got the rpm's high enough (centrifugal chain tension i'm guessing) Mine's a 97 with about 21K.