The concept

The Eagle, revolutionary when it debuted, came about when Jeep's chief engineer, Roy Lunn, joined an AMC Concord body with a Jeep-like 4-wheel-drive driveline.[1] Such a vehicle was a logical step for AMC, according to then-AMC CEO Gerald C. Meyers, as a second energy crisis had hit in 1979, and sales of AMC's highly profitable truck-based Jeep line, which was not famous for good fuel mileage, plummeted, leaving AMC in a precarious financial position. Because of this, the Eagle provided a low-cost way of bridging the gap between AMC's solid and economical, but aging passenger car line, and its well-regarded, but decidedly off-road focused Jeep line, as the Eagle used the existing Concord (and later, Spirit) automobile platform.
A first in passenger cars, early Eagles came with a true full-time system that operated only in all-wheel drive. The Eagle's central differential was single-speed (no low range option) and used a thick viscous fluid coupling for quiet and smooth transfer of power to the axle with the greatest traction, on wet or dry pavement. Similar vehicles made by Subaru and, later, Toyota, only had part-time four-wheel drive systems that could not be engaged on dry pavement.
As the first mass-produced American passenger car with 4-wheel-drive of any type (much less with a system as advanced as the Eagle's was), automotive industry analysts were taken by surprise at the fact that AMC, a company most had deemed past its ability to produce competitive vehicles, turned the best of what they had into a revolutionary, novel, and all-around competent vehicle. In doing so, the small American manufacturer was seen as having cleverly pioneered a new market segment - one that would grow wildly over the next 25 years and beyond, as evinced by Four Wheeler magazine's conclusion in 1980 that the new AMC Eagle was, indeed, "The beginning of a new generation of cars."[2] Indeed, the Eagle's basic concept - that of a station wagon with AWD, raised ground clearance, and rough-road capability - has inspired vehicles like the Subaru Outback line, the Audi Allroad, the Volvo XC range, and many others.