So today I noticed a rattle coming from my I-6 when under load, getting louder when in a higher gear or giving it gas to 3 grand.

Now my truck always had this rattle before, when i geared down on a slope and lasted a few seconds and it never bothered me, but i never heard it when speeding up. Took off my belt, checked water pump, alt, air pump, tensioner and steering pump but all the bearings are good and nothing seemed to be loose. Clutch fan turn just fine with no play.

Any idea where to look next or is it internal? Doesn't sound like a bearing. I'm thinking that maybe my timing gears may have some lashing going on. The only thing i did today was tighten my distributor cap adjustment bolt but i didn't move it out of timing.

 

The timing gear is always under load so thats probably not it, is there a vibration? possible ujoints or bad motor mounts.

 

No theres no vibration, it just gets louder as you get into a higher gear and give it gas. Its a loud high pitch rattle noise that you can't hear when idling or when revving, only while speeding and shifting in higher gears under load, if i coast in that gear or give it little throttle no sound at all.

Its the weirdest thing, no performance lost, no new codes or anything looks out of place. I know my exhaust needs a new O-ring for the manifold and i thought that could be it, but its not loose either. I'm having a hard time where to look next.

And its definitely coming from the under the hood, not the tranny.

 

Best way to described the noise like my GF said this morning, it sounds like someone poured gravel down the exhaust of an old Massey Ferguson tractor.