UA80 eight-speed whine — now on higher-mileage 2021s
CoveredThe 2021 gas Highlander uses the same eight-speed automatic as 2017–2019, and its most-reported problem is the same: a high-pitch whine on acceleration that dealers diagnose as internal transmission failure. On 2021s the complaints cluster at roughly 65,000–127,000 miles — past the powertrain warranty for many owners — with replacement quoted around $6,000–$8,000. Owners cite Toyota bulletin T-SB-0008-21 and a warranty extension. A whine that rises with acceleration on the test drive, unchanged by a scan-tool reset, is the tell; if the car still has transmission coverage, that changes everything, so verify it by VIN. This does not affect the Hybrid, which uses a four-cylinder and an eCVT (electronically variable transaxle — no clutch or torque converter).
Sources: NHTSA complaint database, 2021 Highlander + Highlander Hybrid · NHTSA manufacturer communications (transmission bulletins, recall documents, CSP 22TE09) · Independent mechanic channel transcripts (Car Care Nut current-Highlander review)