Here’s a post from another forum that deals exclusively with the 1st gen Tacoma frame issue:
Toyota Extends Rust Coverage To 15 Years
And a paragraph or two of my perspective on the deal. I copied this from a thread right here several years ago. This is not an issue.
Here's the poop on the Tacoma/4runner difference.
I also had a 98 Tacoma TRD that I purchased in Bozeman, MT in 2007. The frame was rust free. I live in SE WI where road salt is over-applied in an effort to compensate for poor drivers. After being involved in a rear-end/billiard ball/front-end collision on I-43 downtown Milwaukee last winter, I had my frame inspected prior to repair. The truck failed, and I also was compensated at 150% book value by Toyota.
Apparently, the final assembly for 1st generation Tacoma trucks was done in Fremont, CA. The frames were manufactured in Mexico by a subsidiary of the Dana Corp. There were steps skipped in the production that covered the corrosion protection of the metal. Toyota won a huge lawsuit with Dana a couple of years back relating to this quality error. As generous as Toyota appears with the buyback campaigns that followed, the money came out of Dana Corp's pocket (not that it shouldn't; They screwed up.).
The 3rd gen 4runners were assembled in Japan, and the necessary rustproofing was applied to the frames. Rust can still compromise the frames over time on our T4Rs, but it does not progress nearly so fast as the same vintage Tacoma trucks. My Tacoma went from clean to rusted through in four years!