Clutch chatter/ pinging noise 05 Taco

Hello! Haven't been on the forums in a while, but I just purchased my third Tacoma and have a few questions. Its a 2005 6MT 4.0 SR5. While test driving it (I know I should've paid more attention) I didn't notice the noise, but once I got home (3 hours away) I heard a faint noise when giving the truck gas in 2nd and 3rd. It sounds like a metal chatter, almost like something is vibrating at a certain RPM (1200-1500), then it goes away. My first thought was clutch chatter, but it doesn't happen when I am using the clutch (can clutch chatter happen when the clutch isn't being used?). Like I said before, it only happens under load at around 1200-1500 RPM. So far I have removed all heat shields as a first step, although the sound is still there. Is it possible it could be one of the joints in the driveshaft? I checked the main driveshaft and saw no grease zirks, so I may just grease the ones I can find. Also, I noticed the carrier bearing has a decent amount of play in it, could that possibly be it? I put the rear end of the truck on jacks in my shop but it refuses to make the noise when there is no actual load on the tires, which is why it points me to either the driveshaft or something internal in the transmission. I'll get a video of it as soon as I can, thank you.

 

Engine knock/ping?

try some 94 octane gas and see if it goes away

 

I saw a few people saying that, but the noise defiantly sounds external to the engine. Highest we have here is 91, ill give it a go.