Massive rear bumper/tailgate rust

Strange patterns of rust.

Almost looks like the truck was, as others suggest, either left parked IN saltwater for an extended period (probably it would take months,) or regularly parked in/near some kind of industrial process plant where there is a constant stream of acidic vapors.

It looks like the frame was replaced completely (probably under frame-replacement TSB,) while other driveline components not covered by the TSB were left as-is. (Driveshaft, rear diff housing, etc.)

Go to a trusted mechanic (or find one) for a thorough evaluation.

 

The replacement frame and underside doesn’t look too bad. I don’t recall the tailgate hinge pins being a bolt in affair. I believe they are welded to the structural part of the bed. Check that: I just looked at my ‘13 and, yes, it appears to be welded to the structural upright. You’d need to source at least those parts. The quarter panels bolt on to the bed so you *could* reuse those.
While you’re at it, you really should treat the frame and underside of the truck with a rust inhibitor of your choice. Fluid film and wool wax need to be reapplied typically yearly. Cosmoline and Amsoil HD Metal Protect (which I use) can go longer without reapplication. Spray inside of the boxed section up front under the driver’s and passenger’s side too. If you have a hitch, it’s probably toast too. The bumper mounts to the hitch and then that assembly mounts to the frame. If you don’t have a hitch, the bumper has different brackets and mount directly to the frame.

 

If the truck is still subject to "daily use on often muddy gravel roads", I would just park on top of a lawn sprinkler every night and let it sway back and forth and rinse everything off. Can't be any worse than letting that wet gravel stick to and rot everything underneath.

 

Thanks everyone. I've got some heavy decisions to make.

 

I would start having the truck woolwaxed asap. Frame looks pretty good from the pictures.

If your in the northeast I'll have a bed available this winter. I think its in pretty good shape other than the composite part being cracked

 

i thought it was compacted clay mud...

 

same here, I expected the whole frame to look like the crumbled bumper.

that truck looks to be worth fixing. get it cleaned up underneath with a pressure washer, etc and then get it fluid filmed or wool waxed.

 

Based on the few pics in this thread, youll need a new Rear Cross Sill for sure. New bumper, probably new brackets to bolt the bumper on, and certainly all new hardware. Im guessing a new tailgate too?
https://www.toyotapartsdeal.com/oem/toyota~sill~rear~cross~65240-04161.html

Other things to consider:
-Looks to me like that rear diff is starting to rot and has a pin hole leak in it somewhere on the drivers side. Hence the build up of oil and dust.
-Im shocked how good the underside of the cab looks.. How do the rockers look on both sides?
-Certainly expect labor charges to be above and beyond what this job would normally take due to all the rust.
-On that note, expect other incidental costs to pop up along the way due to broken hardware, brackets etc. I believe the entire bed assembly and both fenders have to come off to get the sill out

-And for the love of god, start fluid filming that new frame and cab!