Truck Noize

[sdb479jr]

Started hearing a weird noise coming from the engine that sounds sort of like detonation from cheap gas, but not exactly. Used 87, 89, and 91...all the same. It is more like a clatter/rattle. It does not make this noise on idle, and only does it below 40 mph, especially when accelerating slightly.

If I accelerate moderately or hard, the noise also disappears.

Thanks

2000 Frontier V6 VG33