The new diesel seems to suffer few of the tradeoffs associated with oil-burning engines of the past. There is practically no smoke, and very little noise or vibration. The technology is European, with a very high pressure fuel injection system that burns much more cleanly than earlier designs. There is no warm-up period before starting, because the glowplugs are electronicaly controlled. The turbocharger is an advanced design with variable-geometry vanes that delivers significant induction improvements at both low rpm and high rpm, and at high altitudes.
The Diesel gets the stronger five-speed electronic automatic, which benefits from advanced logic. The transmission, depending on throttle input, can deliver two separate second-gear ratios, a lower ratio for quicker acceleration, a taller one for smooth downshifts.
The Liberty doesn't ride as smoothly on the road as a Ford Escape, particularly over bumps and other irregularities where it bobbles a bit. Nor does it handle as well as the more car-like SUVs. Steering effort is relatively easy at low speeds for a 4x4, nice when parking. On the road, the steering is reasonably on-center, a benefit of its power-assisted rack-and-pinion design. But the long-travel off-road suspension, set up to absorb impact without being overly harsh, makes for lethargic transient response in lane-change maneuvers. That said, the Liberty rides reasonably well for a short-wheelbase 4x4. It doesn't beat the driver up as much as a Jeep Wrangler does. The wider tires of the Limited and Renegade models seem to offer more stability than the narrower tires of the Sport. We've found the Liberty handles winding Virginia backroads well and feels fine on the crowded freeways around Los Angeles.
We've found the Liberty capable of handling fairly gnarly trails. We've crossed steep ditches and gullies, where its short front and rear overhangs paid off. Its tight turning radius is helpful where space is limited, something we discovered while weaving through a stand of tightly spaced trees. We clambered over big rocks and fallen trees and slowly forded boulder-strewn creeks with 18 inches of rushing water. (Jeep says it can handle 20 inches at 10 mph.) Its traction up steep, muddy banks was impressive, with no wheelspin.
Keep in mind, however, that the Liberty is limited by just 6.4 inches of front ground clearance, about the same as a Subaru. Rocks will contact the skid plates, a sound we experienced although we suspect no harm was being done. Another aspect serious trailblazers should note is that the Liberty platform is less upgradeable than Jeep's other 4x4s, such as the Wrangler or Grand Cherokee. However, a locking rear differential is available as a factory option ($285) for the Liberty, and in truly slippery situations, it makes a big difference. If you need a small SUV with the guts to occasionally negotiate irregular terrain or slog down muddy trails, the Jeep Liberty is a good choice.
Four-wheel-drive models come standard with Jeep's tried-and-true Command Trac part-time system. It works great. Shift from 2WD to 4WD on the fly with a slight pull on the hand lever. When the trail is looking really ugly, slow to 2 or 3 mph and while still coasting, shift into neutral, and pull the lever up higher for low range. One complaint, or at least one aspect, of the system is that it's not meant for use on dry pavement, where the wheels bind up when accelerating out of a tight corner. You'll want to shift back to 2WD when you're on solid road.
Selec Trac is an optional system ($395) that offers the modes above but adds a planetary center differential that lets the driver shift into full-time 4WD for year-round conditions. The full-time mode is ideally suited to inconsistent conditions: patches of ice, gravel roads, wet, slippery roads. It also works on dry pavement.
Like most small SUVs, Liberty follows the trend away from body-on-frame to unibody construction. Jeep calls Liberty's construction "uni-frame" because it's a beefed up unibody with frame-like reinforcement rails. This gives the Liberty increased strength and rigidity. That rigidity allowed the chassis engineers to finely tune the suspension without having to compensate for a Flexible Flyer-type chassis. The Liberty suspension uses coil springs at all four wheels. Breaking from Jeep tradition, the front suspension is independent, like the new Grand Cherokee, with forged steel control arms.
For a better off-road ride, Liberty offers eight inches of suspension travel. Short front and rear overhangs (the distance from the tires to the ends of the vehicle) allow steep angles of approach (38 degrees) and departure (32 degrees) in the rough stuff, so you won't be dragging the front bumper in gullies, or even in New York City parking garages. The Liberty approaches the capability of the Grand Cherokee and it will go many of the places that a Wrangler, the king of off-road vehicles, can go. The difference is that the Liberty is more of an occasional off-road prowler, while the Wrangler is built to last in that environment. Still, the Liberty is more at home in the rough stuff than the Escape, RAV4, or most of the bigger SUVs such as the Ford Explorer, which are quickly left behind in really challenging terrain, spinning their wheels and banging up their rocker panels.
