Coolant-bypass pipe leak and six-speed automatic feelmoderate
The V6's plastic coolant-bypass pipe behind the engine can still crack — check the passenger side and top of the transmission for a coolant trail; it's a labor-heavy job, covered under powertrain warranty while in term. The six-speed automatic's low-speed surging and shift feel are quieter than the launch years; a Toyota master tech ties the surging to an engine-computer (ECM) software update and torque-converter shudder to transmission-fluid condition. Toyota's 2019–2020 service bulletin for the V6 addresses lack of power and shift hesitation with a logic update — so a hesitant 2020 is usually a software fix, not a failing gearbox. Keep the fluid on a 60k/6-year schedule.
Sources: NHTSA complaint database, 2020 Tacoma · Independent mechanic/owner channel transcripts (3rd-gen Tacoma, incl. The Car Care Nut)
several thousand
Coolant-bypass pipe (out of warranty)
low cost / routine
ECM update / fluid service