American Motors Corp. didn't have the time or money to subject the Jeep Cherokee XJ — the first modern SUV — to a traditional Detroit-style durability testing program ahead of its late 1983 launch.
Besides, none existed for an off-road vehicle with the XJ's pioneering "uni-frame" body.
But in speaking to author Martyn Schorr in 2015, Cherokee chief engineer Roy Lunn explained how his engineers knew the new Jeep had the right stuff. Lunn, who died Aug. 5 at age 92 in Santa Barbara, Calif., following a stroke, told Schorr he secured credentials for his engineering team to take two preproduction Cherokees on the punishing Paris-Dakar Rally.
Lunn's team prepped the Cherokees not to compete but simply to run the brutal 6,200-mile desert course so the engineers could monitor how the underpinnings held together over some of the world's harshest terrain.
Both vehicles needed only frequent replacement of the shock absorbers and finished the rally in good condition. Lunn knew his groundbreaking design, which featured a steel ladder frame welded to a unitized body, was robust enough to take almost anything consumers were likely to subject the Cherokee to.
Last year, before his induction into the Automotive Hall of Fame, Lunn told Automotive News the fuel shortages and price shocks of the 1970s influenced his thinking on the Cherokee's technical design. "I chose unitized [construction] because it is stronger pound for pound, and it is lightest for meeting fuel economy requirements," he said.
The most fuel-efficient Jeep Cherokee, a two-wheel-drive model with a 2.5-liter four-cylinder engine and manual transmission, was EPA-rated at 24 mpg city and 33 mpg highway in 1985 — figures that rivaled many family cars at the time.
The Cherokee not only was a monster hit for American Motors and later Chrysler — more than 3 million were sold globally before production of the Cherokee XJ ended in 2001 — it also became the template for the modern SUV, and its basic body design continues to be copied by virtually all major global automakers.
"What's amazing about Roy is he had a laser focus on what the issue or problem was, and he put all of his energies and thoughts into making it right," said Schorr, who met Lunn in the mid-1960s.
The four-wheel-drive Cherokee offered rugged off-road capability but felt and behaved more like a car. It had a high ride height but low floor for easy entry. Earlier SUVs, such as the Ford Bronco, Chevrolet Blazer, Land Rover Series 1 (later called Defender) and other competitors were body on frame, or truck-based.
"The unibody was 400 pounds lighter than the competition," said Chris Theodore, who briefly worked with Lunn at AMC and later became Chrysler's vice president of platform engineering.
"The other key to the Cherokee was the four-door model," Theodore told Automotive News. "Competitors quickly copied four doors when sales took off, but it took a long time for them to switch to unibody."
The Cherokee was not the first time Lunn led a team that created a groundbreaking product. Nor would it be his last.