Chugging noise when letting off the gas in my 2001 Expy

[laiod]

Hello all. Just the past day or so my expedition began making this awful chugging noise only when I let off the gas. I've attached a video that has the sound in it (skip to about the 23 second mark to first start hearing it).

Scouring the internet there's been multiple sources saying it could be the pinion bearing? If you guys have heard something like this before please let me know. Luckily I'm able to have the truck sit for as long as need be.

 

[Yupster Dog]

I've attached a video that has the sound

The exhaust manifold is loose from engine block. Probably because of rusted out bolts.

 

[laiod]

Sorry, I forgot to say it’s coming from the rear end and I can feel it in the truck. It’s got a really low pitch to it. I’ll still take a look at the manifold bolts. Thank you.

 

[laiod]

Addition: I wanted to include a link to another video I made, except this one is from the underside of the vehicle. You can clearly hear like a metal rattling noise near the rear differential when it’s moving forward (towards the top of the screen).

I haven’t had a chance to check out the fluid yet but that is clearly leaking as well.

 

[Yupster Dog]

I haven’t had a chance to check out the fluid yet but that is clearly leaking as well.

This