Ford still has a constant speed drive in their Freestyle and at least on of their hybrids. I don't know how it works, but it feels wierd!
Continuously Variable Transmission (CVT)What it is: A continuously variable transmission is an automatic that can select any desired drive ratio within its operating range. Unlike a traditional three, four, or five-speed automatic transmission, the CVT is an "infinite speed" transmission. It continually selects an optimum overall drive ratio between engine and drive wheels for all operating conditions, whether accelerating or cruising. Unlike conventional automatics, there are no perceptible shifts. During maximum acceleration, the drive ratio is adjusted to maintain peak engine horsepower. At a constant vehicle speed, the ratio is set to maintain an optimum balance of fuel economy and driveability. A CVT provides smooth, fast acceleration and high cruising efficiency with the convenience of an automatic transmission. How it works: The most common CVT design uses a segmented metal V-belt running between two pulleys. Each pulley consists of a pair of cones that can be moved close together or further apart to adjust the diameter at which the belt operates. The pulley ratios are electronically controlled to select the best overall drive ratio based on throttle position, vehicle speed and engine speed. Customer benefit: Performance, fuel economy improvement and smoother operation.