As with the rusting Tacoma frames, the Tundra members in question were made by Dana. Importantly, though, the Tundra examination is focused only on "the cross member that supports the spare tire -- not the entire frame." Still, that area has been blamed by consumers for the spare tire coming loose, and for brake system failures due to corrosion at the brake line mounting points.
Toyota ended up buying back Tacomas or extending warranties to settle the rust issue, but Tundra frames were built at different Dana plants and to different specifications, so the Tundra issue is not assumed to be the same as the Tacoma issue. Toyota had until last week to submit its information on the frames, now the NHTSA will need to decide what to do next.
[Source: Automotive News - Sub. Req.]