I would agree that getting that low is dangorous but shouldn't blow it. Mine as well made no noise prior to this other than when I tryed putting senthetic (ms?) in it and it made a tapping sound similar to this one. This one seems worse.
Where is that tensioner so I can check that out?
Also add this into the mix that at 2500 rpm's the noise goes away until it drops below that mark again. Does that noarrow it down to what it may be.

Thanks for the responce and looking for more.

Carl

95.5 Isuzu Rodeo
3.2 Automatic 4x4
High flow cat.
Dynomax muffler
Calmini high flow intake
Independent 4x 3" Body Lift
305/70/R16's Dunlop Mud Rover M/T's
Indy 4x 3" Suspesion Lift