- 1998–2002 Factory-verified
Also described as Transmission, Hydra-Matic 4L80-E, 4 speed automatic, electronicTransmission, automatic, 4 speed, HMD, 4L80-ETransmission, 4-speed automatic, heavy-duty, Hydra-Matic 4L80-ETransmission, automatic, 4 speed, heavy-duty, Hydra-Matic 4L80-E, electronic controls
Also documented for ChevroletHummer
Documented applications
- 2003–2010 Factory-verified
- 1998–2000 Factory-verified
- 1999–2007 Factory-verified
2005–2007: heavy-duty models only (GM’s HD list)
- 2001–2007 Factory-verified
- 2007–2008 Disputed
printed in the 2007–2008 lists only; the 2009 list prints MYD disputed: the 2007 and 2008 new-body Sierra lists print it in the heavy-duty half, but that half repeats the 2007 Sierra Classic heavy-duty list (same codes, same order) and no other source names the GMT900 HD gearboxes, so it may be a Classic carryover; both readings kept
- 1998–1999 Factory-verified
Wikipedia names automatic transmissions only
- 1998–1999 Factory-verified
Wikipedia gives a 4 speed 4L80E automatic for this generation
- 2000–2006 Factory-verified
only in: Yukon XL 2500; Wikipedia (Chevrolet Suburban) names it for the 2500 with the 6.0L
This page aggregates every documented appearance of MT1 in the GMC reference. Confidence and citations are shown per application — the same code can be better documented in one year than another.