The 1984 was such a dramatic redesign, it somehow made its predecessor from one model year prior, the , look like it belonged in another century. I know this, because I just drove both back-to-back; the SJ is, comparatively, a pile of junk.

The Jeep Cherokee XJ will go down in history as one of the greatest SUVs ever built, with Jeep selling a whopping 2.9 million between 1984 and 2001. “It needs to be said: The 1984 Jeep XJ Cherokee and Wagoneer, the most completely redesigned Jeeps since 1963, were the most advanced four-wheel drive vehicles in the world,” Patrick Foster says in his book Jeep: The History of America’s Greatest Vehicle.

“Everything about them was new, and they introduced more new technology to the SUV market than any vehicle before or since,” he goes on. The new XJ Jeep (which came in “Wagoneer” trim) was 1,200 pounds lighter, 21 inches shorter, six inches narrower and four inches lower than the Cherokee SJ it replaced, and yet—thanks to unibody construction—the XJ kept 90 percent of its predecessor’s interior volume.

Fuel economy was—thanks to the smaller size and lower weight, as well as downsized engines and an extra gear on the manual trans—phenomenal, with the 1984 XJ managing between 16 and 21 MPG combined in . By contrast, the 1984 Jeep Grand Wagoneer, which was mechanically identical to the Jeep Cherokee XJ’s predecessor, the SJ Cherokee, . That’s downright pathetic.

I noticed just how drastically the XJ and SJ differ when I drove the two back-to-back yesterday. Having just gotten my up and running—and also having daily-driven my (which is quite similar to the Cherokee) for the past three months—I had gotten used to piloting an SJ.

But after jump-starting my ’s dead battery and inflating its tires after letting the SUV sit for the winter, I took to the streets, pressed the pedal down, and found myself in total awe. “How is this even remotely related to that 1979 Jeep Cherokee SJ?” I wondered. “This is better in literally every way!”

The venerable 4.0-liter engine (which found its way into the XJ line in 1987 after the Jeep debuted with a carbureted 2.5-liter inline-four and a garbage 2.8-liter V6) is powerful and smooth, making 190 ponies thanks, in part, to Chrysler fuel injection.

It’s a reliable, easily-serviceable engine, and, even when bolted to the tough Aisin-Warner AW4 four-speed automatic—it makes the 3,300 pound XJ feel quick. It also manages about 15 MPG in the city, and around 18 on the highway in stock form; my lifted one, with its bigger tires, does about 12 city, 16 highway.

The SJ’s 5.9-liter V8, built at the same Kenosha, Wisconsin plant as the 4.0-liter, supposedly makes around 175 horsepower, but it feels like quite a lot less, thanks in part to the three-speed slushbox it sends power through and thanks also to the two-barrel Motorcraft carburetor managing the air and fuel.

Lugging around 4,300 pounds of body-on-frame Jeep, the Cherokee SJ feels slower than pretty much any I’ve ever driven. And with its horrendous 10 MPG in the city and 12 highway, along with the engine’s ridiculously finicky emissions-controls equipment, it’s quickly sending me to the poor house.

But the XJ isn’t just quicker and more efficient, it’s also much more comfortable and much more competent in the corners than the SJ Cherokee (It’s worth mentioning that the SJ Grand Wagoneer is pretty comfy, too). The XJ’s bucket seats with headrests are awesome, and its five-link coil-sprung “Quadra-Link” solid front axle gives a smoother ride and way better handling than the heavy SJ’s leaf-sprung dual solid axle setup.

Articulation is also better, as is ground clearance, as well as approach, departure and breakover angles. These, along with its smaller profile, make the XJ better both off-road and on.

Obviously, the XJ wasn’t perfect. Getting into the rear seats was difficult thanks to a narrow door-opening, and the XJ also dropped one of the SJ’s coolest features: a rear tailgate with power glass. Plus, the classic, boxy XJ is arguably not quite as pretty as the SJ, which was based on the 1963 Wagoneer designed by the legend, .

Still, after wrenching and driving both vehicles, I couldn’t help but be amazed at how much better the XJ was than its predecessor. I can’t think of a recent redesign as drastic as the XJ-SJ transition (perhaps the current-generation Explorer?).

The SJ is based on a body-on-frame platform that has roots all the way back to the 1963 model year, so when AMC debuted this smaller, unibody XJ for 1984, it shocked quite a few diehard Jeep fans. “Blasphemy!” many of them likely cried. “That’s not a REAL Jeep!”

But in time, especially after Chrysler fuel injection showed up in 1991, it became clear that the drastically redesigned XJ was superior to its SJ predecessor in a big way—so much so, that most folks have forgotten that the two are even related. And after driving them both back-to-back, I totally understand why.