Frame replacement

I had my frame inspected as per recall notice several years ago. Was told it was "ok". Recently replaced parking brake assy (was rusted/frozen), manifold back exhaust, and a few other items down under. Noticed severe flaking/rusting out (but not "through") yet. Any suggestions on how to get Toyota to fix this?

 

I’m far from an expert on this, many here know more than me on the subject, but from my research on this if Toyota did an inspection and treatment already they won’t do a frame replacement.
My truck got the underspray treatment before I got it (with the original owner), and I found it to still have a fair amount of rust going, nothing I would call scary, but flaking in places, and just generally getting going on a lot of areas.

I just spent about 4 days under the truck, I scraped all loose rust I could, everywhere I could reach, used a wire brush wheel on a drill everywhere I could reach, and a hand wire brush anywhere else I could reach.
I followed that with rust converter spray, then a few coats of black spray paint (spend the money, get Rustoleum, I got the ‘professional’ grade and it was worth it, you want one that sprays at all angles, also used some cheap paint when I ran out of the good stuff, and it was thin and not nearly as good), then I put a heavy coat of asphalt undercoating, then I covered everything underneath with a film type treatment (I used Rust Check). Hoping this is good for my ownership, and I’ll keep up on the film treatments as needed.

You could try Toyota with yours, but I doubt they’ll want to do anything, especially if it hasn’t really failed yet. I would recommend doing some serious maintenance like I did.

 

Unless the rear cross member recall wasn't performed on your truck your pretty much out of luck.

The service campaign which is what most of the frames were replaced under ended after 12 years from the in service date of the truck. The thing was the undercoating fulfilled the campaign if there were no holes. It's a one and done affair.