2001 3.4l 4WD Gnashing Sound When Accelerating

My 2001 Doublecab 4WD 3.4l automatic with 224k miles started making a strange noise recently. I have a poor iPhone recording for those who care to invest about 30 seconds:
https://u.pcloud.link/publink/show?code=XZhCQBVZU4PF9PdHLlL75GuznjrqJBudyQ57 In the recording you can hear my blinker twice (I drove a block in between) followed almost immediately by the sound at issue. My first thought was loose heat shield, but I haven’t found one. I will be checking the exhaust system for loose clamps next. It is definitely a metallic sound.

It is making the noise only when I accelerate and almost exactly at 1500 rpm. It sounds normal before and after. It will not do it if I am parked and rev the engine. It does not do it at highway speed. I haven’t noticed any loss of power or issues with shifting. My greatest fear is something transmission-related.

Anything else I should check? Any similar experiences? Thanks in advance!