General Motors 2ML70 (Two-Mode)

General Motors' Two-Mode hybrid transmission — in the hybrid Tahoe and Yukon.

It is not an automatic with a motor bolted on. Two electric motors sit inside the case alongside a four-speed planetary gearset, and the transmission can behave as a CVT at low speed and as a fixed-ratio automatic at high speed — which is what two-mode names, and why the catalogue's own rows describe it contradictorily as both.

That makes symptom interpretation genuinely different. A hesitation, a shunt or a change in engine note at low speed may be the transmission, or it may be the mode transition or the engine's own cylinder deactivation — three systems that feel similar and are unrelated. A scan showing no transmission fault has not exonerated it.

Its expensive failures are the motor windings and the power electronics, not the gearset, and they present electrically: a warning, reduced power, or a refusal to start the engine.

It was built in small numbers over five years, so specialist knowledge is thin and a general hybrid diagnosis is more likely to mislead than help. Establish the transmission before applying anything written about hybrids in general.

⚑ The front-drive two-mode is the 2MT70 and is a different gearbox. It was built for the transverse cars — the Vue and the Aura — where this one is longitudinal, behind the engine of a full-size truck. The catalogue does not hold the 2MT70, and a listing that offers one for the other is offering a unit that will not fit.