So you thought my rattling/ticking noise was an exhaust leak?

It's hard to tell by the video exactly what the noise is but it wont hurt to drop the rear diff cover and at the very least change the oil and replace the pinion seal. It looks as though it has been leaking for quite some time. While you are doing that, drop the drive shaft and feel how smooth the rear U-joint rotates on each cap and feel how smooth the ball and trunnion rotates through its range of motion. Drive shaft noise can "travel" down the shaft causing a "tinny" sound. I think you are going to find that noise in one of those components.