Clicking/Tapping Sound Vs. Engine Speed

[irontodd]

This weekend, I started hearing a minor clicking/tapping sound coming from my 99 TJ. I've only got about 78K miles on it, so I poured a quart of engine cleaner in & then changed the oil. After putting about another 20 miles on it, the Tapping got a LOT louder. The sound is definitely based on engine speed. It's a 5 speed manual, and the sound happens in N and in 1-5 gears. The sound also happens whether the clutch is engaged or disengaged (pedal pressed or released). As I throttle up, the sound gets faster/more frequent, but it always happens at regular intervals relative to engine speed. Oddly, after crawling under my Jeep, it sort of sounds like the sound is coming from inside the bellhousing (between the engine and tranny) where the flywheel and clutch would be. Is there anything in there that would create this sound if it was bad? I have never worked on a clutch before and am trying to determine what I'm getting myself into.
Thanks for your comments!