Aisin TL-80SN (AA80E)

Aisin's longitudinal eight-speed — the first eight-speed automatic in a production car, in the 2006 Lexus LS, and afterwards under a remarkable range of badges: the Lexus GS and IS, the Audi Q7, the Porsche Cayenne and Panamera, the VW Touareg and the Cadillac CTS.

It carries three names and they are all the same gearbox. Toyota calls it the AA80E, Aisin the TL-80SN, and the Volkswagen group the AL551 — with the rows on this site often printing TL-80SN/TR-82SD. So a Porsche owner and a Lexus owner researching their eight-speed are researching one transmission, and neither is likely to be told so.

Its faults are hydraulic and electronic rather than mechanical. The valve body and its solenoids account for most of them, presenting as a harsh or delayed engagement, a flare on one change, or a limp mode — and on the German cars particularly, the fluid was presented as lifetime and is not.

A torque converter shudder at light throttle is the other recurring item, the same lock-up symptom shared by every modern automatic here, and it tracks fluid condition closely enough that a service is a diagnostic step.

It is not the ZF 8HP, which sits in the same class and in some of the same cars' siblings; the two share a ratio count and nothing else.