2021 Jeep Grand Cherokee L WL Platform Deep Dive

Managers on hand at the unveiling of the 2021 Jeep Grand Cherokee L were uncharacteristically silly about their new baby’s architectural lineage, as if loose lips risked sinking their newly christened ship. Now that trucks are rolling off the newly renovated Detroit Assembly Complex Mack plant, Jeep veep Jim Morrison has finally revealed some family tree details about the Grand Cherokee’s all-new WL platform.

A completely new platform

Okay, there is nothing completely new under the sun, and surely some bolts, bits and bobs carry over, but Jim swears that this architecture mainly started from a clean sheet. The team that designed it was, of course, well acquainted with the Giorgio platform that underpins the Alfa Romeo Stelvio (and Giulia since) and will probably create the Maseratis Grecale SUV. But the engineering that is appropriate for a large SUV (and sports sedan) does not necessarily facilitate a skilled train ride over the Rubicon Trail. This WL is optimized for safe off-road driving, for handling payloads and towing loads that are close to the top of its class, and for easier access to the cabin.

Sophisticated suspension

At the front, the lower steering arms are replaced by pairs of ball joint links, so that now when you turn the wheel, instead of just turning around a fixed “king-pin axis” defined by drawing a line through the two ball joints, the knuckle sweeps the shape of a con. This “virtual” steering axle has the effect of reducing or eliminating the scrubbing radius (determined by the distance from the center of the tire’s contact surface to the point where the steering axle comes into contact with the ground). The result is that the new arrangement promises an improved sense of stability. On the back there is a revised configuration with five links.

Adaptive damping with air suspension

The Quadra-Lift air suspension now comes with adaptive dampers (active damping was strictly reserved for SRT and Trackhawk models in the WK2 Grand Cherokee). This pairing provides a more relaxed ride, especially during abrupt transitions, either left and right or between different surfaces. And to prevent the intake of dust when you are out on the trail, the air suspension system is completely closed, and a couple of new air tanks at the back under the seat on the third row means that it drops faster to the access height and falls 1.8 inches in seven seconds without releasing any air to the surroundings.

Higher strength, lower weight, stiffer structure

The WL platform makes its debut in its expanded form – 15.1 inches longer in total than the WK2 model on a 7.0 inch longer wheelbase – to accommodate a whole extra row of seats. And if you compare similar trim levels, the difference in service weight between the outgoing WK2 two-row Grand Cherokee and the new L is 68 pounds or less – within 1 percent. This was made possible by increasing the use of high-strength steels (now only 29 percent of the unibody structure is constructed of mild steel), and by increasing the use of aluminum. The front struts are cast in aluminum, while several other parts are composed of aluminum profiles and castings: strut struts, front suspension and driveline cradle. The hood is also aluminum (as before). The body is 13 percent more resistant to twisting, which Jeep owners can notice when they place a tire on a large rock, and it is 18 percent stiffer in bending (useful when driving over the jump). Improving these numbers becomes more difficult as the “box” gets longer.

Identical fuel economy

Buy a 2021 Grand Cherokee and you get an EPA-rated 19/26/21 mpg with a V-6 and rear drive, 18/25/21 if you choose 4WD and 14/22/17 mpg if you run for V-8 4×4. And those numbers apply just as much, whether you make a deal on the outgoing WK2 platform with two lines, or choose the new, long WL version. (Expect next year’s WL two-row GC to do even better.)

Keeping the line on mass helped, but some other techniques made a big difference as well: All 4×4 models get an active transfer case that disconnects the drive to the front when not needed, which reduces parasite losses. Active grille hatches improve aerodynamics, as well as extensive aero-shielding of the chassis on models without the terrain package’s ski plates. The net result is an improvement of 13 counts of air resistance, which lowers the Cd from 0.370 to 0.357 – that’s more than enough improvement to cover the small increase in front area (from 31.62 sq ft to 31.93 sq ft) that mainly comes with 2.2. -inch increase in width. In total, the “drag area” (CdA) improved by 2.6 percent.

Lower without losing ground clearance

Mounting the front differential directly on the engine helped lower the driveline 1.6 inches, allowing the bonnet line, line of sight, and seat hip points to be lowered slightly. The door sills were also lowered by 0.3 inches on standard suspension; even more with air suspension. But the redesigned substructure essentially retains the minimal ground clearance, which drops 0.1 inches with the standard suspension and gets the same amount of air suspension. But the distances to the fuel tank, front and rear axles are improved by more – 0.7, 0.4 and 0.8 inches for the standard suspension.

Active engine mounts

New motor mounts that can change their stiffness are placed to fit into natural frequency nodes for the entire driveline. This reduces noise, vibration and hardness transmitted from the driveline to the combined body and chassis.

Leave a Comment