Allison products are specified by over 250 vehicle manufacturers and are used in many market sectors, including bus, refuse, fire, construction, distribution, military, and specialty applications.

[3] General Motors began developing automatic transmissions with a hydraulic torque converter in the 1930s under its Product Study Group, offering it as an option for Oldsmobile for the first time in 1940.

Allison designed, developed and manufactured the first-ever automatic transmissions for heavy-duty vehicles including delivery trucks, city buses, and railcars, starting from 1948.

[10] The Allison 850-series torque converter was a crucial component in the post-war development of self-propelled railcars, most notably the Budd Rail Diesel Car, which first went into service in 1950.

[3] Development of the V-Drive transmission was led by Bob Schaefer, an emigrant from Germany who had joined GM in 1942 after helping to lead the Twin Disc Company, which was one of the licensees of the Ljungstroms hydraulic torque converter.

[3] In addition to the transit bus market, Allison began developing automatic transmissions for commercial trucks in 1953.

This effort resulted in the MT-25, which designated the intended application ("M"edium "T"rucks) and maximum input power, 250 hp (190 kW).

[3] Because of the additional cost of the automatic transmission, sales were initially slow until Allison began targeting specific markets that required both on- and off-road driving as well as frequent stops and starts, such as concrete mixing and garbage trucks in the early 1960s.

[19][20] In 2007, GM sold Allison Transmission to private equity firms Carlyle Group and Onex Corporation for US$5.6 billion.

[40]: 4  As installed in buses, the EP System has two operating modes or speed ranges, with the changeover generally occurring between 15 and 25 mph (24 and 40 km/h).

As vehicle speed increases, the input motor begins to dominate,[40]: 18  resulting in nearly total mechanical output only.

[39] Through 2011, GM intended to introduce 16 passenger car and truck hybrid models based on the Allison split-mode system.

[40]: 11 The EV Drive Unit is installed in lieu of a conventional transmission and acts as a continuously variable transmission controlled electronically;[39] it integrates two motor-generators (MG-A and MG-B, on the input and output, respectively), three planetary gear sets (P1, P2, and P3), one rotating clutch (C2), and one stationary clutch (C1).

[40]: 19  The ESS uses nickel-metal hydride batteries, air-cooled using internal fans, and weighs approximately 915 lb (415 kg).

[40]: 23  The DPIM and ESS have been improved since the initial introduction, and newer models generally can replace earlier units.

The "Max" models are capable of operating on electric power alone for up to 10 mi (16 km), depending on the axle ratio and duty cycle.

The first model, 100D, was designated for its gross axle weight rating (GAWR) of 10.4 t (23,000 lb) and (D)ual electric motors; 100D has a continuous and peak power output of 424 and 648 kW (569 and 869 hp), respectively, with a maximum torque of 46,800 N⋅m (34,500 lbf⋅ft).

[47] The Allison eGen Power integrated axle also includes a multi-speed gearbox to optimize both launch and cruising speeds; it was designed to be a drop-in replacement for existing axles for medium- and heavy-duty trucks and buses, allowing more flexibility in battery placement.

For example, the TT 2220 was a twin-turbine 2000 series automatic transmission with two forward speeds and a maximum input torque capacity of 250 lb⋅ft (340 N⋅m).