A simplified, modular, and generic simulation model of an automatic transmission has been developed for use in control system development. This model employs a two clutch concept to simulate the range pack of an automatic transmission. As a result, this model can be adapted to any transmission which relies on clutch-to-clutch (oncoming and offgoing) shift transitions. The model simulates rotating clutches as well as stationary clutches by simply setting the proper gear configuration and ratio around the clutch. The model is capable of continuous simulation of the power train by instantaneous change of gear ratio and associated parameters particular to each shift.Lockup clutch and torque converter models are integrated in parallel and represent the alternative power paths between the range pack and engine. Also included are models of the engine, brake, retarder, and road load. An optional hydrostatic steer model is also incorporated.This model is currently being used as a core for a real time dynamic simulator at Allison Transmission Division (ATD) of General Motors Corporation to facilitate military transmission control system algorithm and logic equation development in the lab environment. Use of this simulator has resulted in a significant reduction in transmission controls checkout time during both test stand and vehicle level controls development testing.