The 6-speed automatic on 3rd-gen Tacoma V6 is notorious for hunting and downshifting aggressively in normal driving. Toyota issued multiple TSBs and a software update.
Test transmission behavior in highway stop-and-go — any aggressive hunting or repeated downshifts = TSB update needed.
Est. cost: $0 TSB software update / $4,000–$7,000 transmission if mechanical
Source: Toyota TSB T-SB-0092-20