IMA (Integrated Motor Assist)
In an effort to improve fuel economy, drivability, durability, and cost, many changes have occurred to automatic transmissions over time. In the last decade however, the proliferation of new models has been unending. Step-type transmissions have ratcheted up the gearing from old-time three- and four-speeds to five- through seven-speeds.
GM’s 2ML70 Hybrid Two-Mode Transmission
GM’s 2ML70 hybrid transmission (Figure 1) is a four-speed unit with fourth gear being overdrive. Applications include the 2008 Chevrolet Tahoe and GMC Yukon and the 6.0-liter 2009 Cadillac Escalade. It also was used for a short time in the 2009 5.7-liter Chrysler Aspen and Dodge Durango. BMW uses the two-mode 2ML70 in its ActiveHybrid X6, and Mercedes-Benz also uses it.