The public relations folks at Chrysler Corp. won't let me tell you how the 1999 Jeep Grand Cherokee stacked up against its soon-to-be corporate cousin the Mercedes-Benz ML320 during some muddy boulder-crunching off-road maneuvering last March in Chelsea . . . at least not for another couple of months.

But here's a good bit of what Jeep engineers told me about their flagship sport/ute before I jumped behind the wheel.

The Grand Cherokee is motivated by the all-new 4.7L SOHC V-8 engine built at the company's renovated Mack Avenue engine plant in Detroit.

The aluminum-headed 4.7L engine replaces the ancient 5.2L all-iron V-8. Despite giving up a half liter of displacement, the new power unit kicks out 5% more horsepower (230 hp in total). It also produces better fuel economy - a combined city/highway average of about 20 mpg (11.8L/100 km) vs. 17 mpg or (13.8L/100 km) for the 5.2L. It also complies with California's Low Emission Vehicle (LEV) standards.

The new SOHC engine (still two valves per cylinder) does give up a piddling 5 ft.-lbs. (7 Nm) of torque to the old OHV 5.2L V-8; new engine: 295 ft.-lbs. (400 Nm), old dog: 300 ft.-lbs. (407 Nm).

Aluminum cylinder heads, a hollow camshaft, magnesium valve covers and a molded composite intake manifold helped shave 54 lbs. (24 kg) off the weight of its predeccesor.

Chrysler says the all-new 45RFE 4-speed electronically controlled automatic to which the 4.7L V-8 is hitched is specially designed for ute-duty with a short first gear for quick getaways and a special, alternate second gear designed to jump in during kick-downs. Also incorporated is an adaptive function to "learn" how the driver wants to drive. The two-speed torque-modulating transfer case is supplied by New Venture Gear, Chrysler's joint venture with General Motors Corp.

The power gets to all four wheels - when necessary - through a totally new differential system dubbed Vari-Lok. The Vari-Lok unit on the front and rear axles (once the Quadra-Drive transfer case takes care of torque differences between front and rear axles) uses speed-sensing "gerotor" couplings to equalize speed between two unequally slipping wheels on the same axle. The gerotor pump sends extra hydraulic pressure to act on clutch packs to transfer more drive torque to the wheel with the most traction. Unlike most "preloaded" differentials, Chrysler says Vari-Lok is wear-free.

Other engines available are the carryover 4L inline 6-cyl. and, for those Grand Cherokees assembled in Graz, Austria, a new 3.1L turbodiesel built by Detroit Diesel Corp.'s VM Motori affiliate in Italy.

John Sgalia, Jeep exterior design studio manager, listened to an echoing refrain from current Grand Cherokee customers urging only minimal changes. So there's no dice-rolling on the styling front.

Indeed, it will take a third or fourth look to capture the full dimensions of the evolution.

Most notably, the seven grille portals are wider and angled a bit more. Headlamps are larger and the corners of the front fascia are rounder, although the overhang from the front tires is the same.

In the rear there is a marginally softer look with a new external central high mounted safety lamp and an integrated door handle.

The big change inside involves shifting the spare tire from the side of the storage compartment to beneath it. That opens up an additional 1 cu. ft. (28.3L), but chops into the fuel tank to the tune of 2.5 gal. (11.3L) to 20.5 gal. (77.6L) from 23 gal. (87.2L).

There will be no side air bags offered.

Despite weight reductions in the powertrain, the complete vehicle is 100 lbs. (45 kg.) heavier than its predecessor, with the 4L engine and 60 lbs. (27 kg.) heavier when packaged with the 4.7L V-8.

Mike Doman, manager of body systems engineering for the Jefferson North assembly plant, says plans are to work up to a line speed of 1,336 vehicles per day, vs. 1,214 per day on the current model. There are nine panels featuring tailor welded blanks, which help reduce the number of pieces and make the body 20% stiffer.

One stamping, for example, now encompasses the body side from the A-pillar to the D-pillar.

Mr. Doman says that although some aluminum or composite body panels were considered, they were not deemed cost-effective in the volumes required for Grand Cherokee.

Other dimensional differences from the model it replaces: the '99 Grand Cherokee is 4 ins. (10 cm.) longer, 2 ins. (5 cm.) taller, 1.5 ins. (3.8 cm.) wider and features a 1-in. (2.5-cm.) lower step-in height. The turning circle diameter is a notable 1 foot (0.3 m.) tighter.

But is it as good as the Mercedes M-class? See our September issue.