Rear rattle-vibration low-speed on rough roads

I have a rear-right side rattle issue, help/suggestions please…it's a long story…
First I have a 2019 DCSB Off Road. From the beginning, I've added weight to the truck, sliders, ARE HD Camper shell, Dave's (wood generation 1) kitchen-style box, and other gear was the first. I installed Firestone air bags to stock suspension before the kitchen box and all was well for over a year.

Then one day I heard a rattle from the right rear. I was able to duplicate it by pushing with my foot on the exhaust, shaking it. The truck was going in for service, the techs looked at it and said the heat shield from the Firestone airbag was bent and hitting the exhaust. They bent the shield back and all was well again.

Added more weight before a trip across the Mojave, Frontrunner racks, 10 gals gas, 15 gals water on the rack. Took a trip in the beginning of March across the Mojave road, and Joshua Tree area and all was well.

Covid hit-truck sat for much of 4 months, not much driving, no trips. Air bags were low on air. Filled them up and took short trip back to Mojave in September, same set-up as in March although this trip didn't drive as much. Camped for a few days then started to head back. Drove on heavy wash-board road and noticed the rattle again. Stopped truck, checked and found airbag on driver side way low. Filled up bag to 90lb, drove on and no rattle…I thought ok, when airbag is low the shields will rattle. Got back to blacktop, rattle back and truck leaning heavily on right rear. I knew I had an air leak in the bags. Filled once more 30 min later and down again within 15 min. Drove home leaning and rattling (about 5 hours).

Had bags checked, right side bag and mount totally destroyed. Shop 1 (that installed the airbags) suggested an add a leaf (aal) and removing bags altogether. I agreed and paid. Rattle still there, I can only hear at low speeds going over bumpy and uneven roads/streets at low speeds…and truck was sagging in the back way too much and bounced like crazy…returned the aal and took the hit on the labor. I knew I needed new leaf's in the rear.

I ordered new Dobbinson rear leaf-packs/shocks and front shocks/springs. While waiting for them to arrive, the truck was due for another service and the fuel pump recall. When I brought in to the dealer I asked them to check for the rattle in the rear at low speeds (5-20 mph) on bad city streets or gravel. They said that there was too much weight in the back and without everything taken out (which I cannot do) they couldn't look at it. I also had too much gas in the tank so I had to reschedule the service. The dealer wanted $200. to check for the rattle/noises. I declined.

Meanwhile, new suspension arrived and I had it installed at shop 2. Incredible ride, no sag, it finally feels like I am driving a truck. Firm and sure-footed…even on stock wheels/tires. Very satisfied with the ride! But, the darn low-speed over rough-road rattle-noise is still there!

Today back at shop 2 for re-torque of suspension and replacement of a broken rci a-arm bash plate (another casualty of the Mojave). I asked them to look at the rattle-vibration noise. I am able to duplicate by using my fist and hitting the inside the fender well...it does sound like a heat shield-ish or loose plastic.

The guys at the shop tell me it's coming from the composite bed. They duplicated it by hitting on the bed. They said they have seen it on Tacoma's (and they work on a lot of them). I didn't fully understand, but something about the composite beds coming apart when they are loaded up? I have searched TW and found nothing like this in my searches…

If you've read this far…any advice? I'm lost, yikes!

 

What?

 

Too much noise!