Rattling Under Hood?

Hey, I have a 2008 Tacoma 2.7L 5speed manual with 206k miles. I just put a new trans into it because the bearings were bad in the old one. I’ve had the truck for 2 months. I have a rattling/ratcheting noise under the hood or under the floor board that happens during cruising rpms, deceleration, and it last for a couple seconds after pushing the clutch in. I have no idea what it is. The fan is not hitting, the u-joints and carrier are both good. It almost sounds like the heat shield is being battered to death. Can anyone tell me what this is please? The only thing I’m not willing to do is take the engine out.

 

Have you checked the heat shields?

 

I’ve checked the heat shields. They seem to be tight on there. Even bent it up to test it again at one point.