Rear rattle on washboard roads?

[MummifiedCircuitry]

When I bought my truck I noticed a loud rattle from what sounds like the left rear, only when going over washboard roads. I removed the rear sway bar, secured the spare tire, and just installed new KYB Monomax shocks, but it's still there. I tried to recreate the noise by shaking parts by hand, exhaust, gas tank, springs seated correctly, removed center hubcap, etc, but nothing feels loose or makes any noise. Has anyone else heard this noise, or it just one of those things to get used to? Video below is from yesterday, after new shocks.
https://www.youtube.com/watch?v=Tgyt8K053M8

 

[Toasty]

Maybe rear door is out of adjustment, mine used to do that and it drove me crazy. They are a pain to adjust, i got mine to quit making noise but it is a little harder to open now.

 

[MummifiedCircuitry]

Mine does take a bit of effort to close, maybe its drooping. How did you go about adjusting yours? Loosen the hinges, raise the door a little and tighten down?
Thanks for the info, I hadn't even considered the rear hatch door.

 

[Eric M]

Make sure the hinges are intact. My top one is broken and the door will squeak a bit over rough roads.

 

[Toasty]

loosen the hinge bolts, realign the door. Then you need to adjust the catch and striker, it's easy to do but there is a lot of adjustment in those things and it takes a small amount to make it not quite right. You may need an impact driver to loosen the striker and catch if you live in a rust area.

 

[MummifiedCircuitry]

After looking at the hatch a bit, I don't think it's the issue. I couldn't even get it to wobble one bit, it's tight and does close properly. I checked the oem toolkit in the rear door for loose parts, but everything was clipped into place. Any other ideas of what it could be? Do the oem body/frame spacers ever go bad on these, could it be the body bouncing on the frame? Thanks again.

 

[nwoods]

To the OP, no clue what the rattle is, though you might try the rear spare tire mount.

To Eroc M, I have a spare set of White hinges in good shape if you need them.

 

[MummifiedCircuitry]

The spare tire rattled on the mount when I got the truck cause the previous owner snapped two of the bolts off. I drilled them out and got three new lugnuts to secure it, it's very sturdy. I'm going to temporarily remove it tomorrow to rule it out. My license plate surround trim that says "mitsubishi" is a bit loose, but I don't think it could generate a noise that loud, it's like metal on metal, I was almost positive it was shocks. Is it possible for a springs to make that sound even if it isn't visually damaged and is properly seated?

 

[Toasty]

It's hard to tell from your video but next you should check your upper and lower trailing arm bushings. Sway bar and links are gone correct?