Automatic transaxle, 3 speed (THM 125C)

Years 1984, 1998 Models 3 Factory citations 3

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Also described as Transmission, automatic, 3 speed, 3T40Automatic transaxle, 3 speed (THM 125)

Also documented for Buick Chevrolet Pontiac

Documented applications

Achieva — N-body (1992–1998)

1998 Factory-verified

platform-list code; no source shows whether the Achieva offered it.

GM factory document — 1998 oldsmobile achieva rpo code list, p.1.

Cutlass Ciera — A-body (1982–1996)

1984 Single-source

matched to the unit by meaning: Wikipedia's Ciera article names the TH-125C 3 speed but prints no code and gives no year for it; only 1984 is claimed, the year the 1984 Celebrity kit heads the code on its own option line (Wikipedia's Turbo-Hydramatic 125 article gives only the platform's span, which does not date this car); from 1985 the kit sells the unit as MX1; shared A-body code; cited from the Chevrolet Celebrity kit

GM Heritage factory kit — 1984 Chevrolet Celebrity, p.41.

Omega — X-body (1983–1984)

1984 Single-source

GM engineering code behind the MX1 merchandising option; matched to the Omega's unit by meaning: Wikipedia's Omega article names the 3 speed TH-125C automatic in its infobox but prints no code; the Citation kit's automatic-transmission weight line for the 2.5 L engine reads "Merchandising Option for MD9, MX1", a remark naming two units, so the year rests on the page's 1984 model-year field and the row stays single-source; 1983 is left out because no listed kit page heads the code that year; shared X-body code; cited from the Chevrolet Citation kit

GM Heritage factory kit — 1984 Chevrolet Citation, p.34.

This page aggregates every documented appearance of MD9 in the Oldsmobile reference. Confidence and citations are shown per application — the same code can be better documented in one year than another.