Approach the 2018 Grand Cherokee Trackhawk and few external cues give away that this isn’t a normal Grand Cherokee SRT. The front fog lights are missing to allow more air to feed air-to-oil intercoolers, the quad-tipped exhaust features a shiny black chrome finish, Trackhawk specific wheels fill the wheel wells, and two Supercharged badges on the doors along with one Trackhawk badge on the tailgate give away what this really is.
Slide into the driver's seat within the leather-lined interior, push the red start button, and you’ll be met with a familiar, albeit toned down growl from the supercharged 6.2-liter Hemi V-8.
Pull onto the street without mashing the throttle and you might get confused, as there’s no supercharger whine. The blower doesn’t start to make itself known until just over 2,000 rpm, and it’s a lower, more gravelly intake sound than you get in other Hellcats.
The exhaust feels like a wet blanket’s been put over it, until you mash the throttle and it wakes up hell. The Hellcat's exhaust bark upon upshifts and downshifts is present, thankfully, though it's still softer and more refined than the bark of the Charger and Challenger Hellcats, in part due to tuned mufflers from the Durango SRT.
Driving the Trackhawk around the city can be just like driving any other Grand Cherokee, as long as you don't tap too deeply into the 707 horsepower under the hood. You can lope around the streets and you’ll probably average about 13 mpg given our experience, so bring your credit card for frequent fuel stops.
Turn toward a freeway on-ramp, look your co-pilot in the eye to make sure they're ready for what is about to happen, stomp the accelerator to the floor, and feel 1.4 Gs of thrust throw you back into the seat as all four wheels grip at the pavement. Blast onto the highway and realize you had best slow down unless you want to see the inside of a jail cell. Hit the brakes and 15.75-inch two-piece vented Brembo front rotors are grabbed by six-piston calipers to bring things back to reality, quickly.
You may be starting to get the idea that the 2018 Jeep Grand Cherokee Trackhawk is a bit different than other Hellcats while also being the world's most ridiculous SUV. You'd be right.
2018 Jeep Grand Cherokee TrackhawkEnlarge Photo
An upgraded Hellcat
Engineers didn't just shove the Hellcat powertrain into the Jeep Grand Cherokee to create the Trackhawk. It required much more than that.
Officials from Fiat Chrysler Automobiles told us the Jeep buyer is a different demographic than the Dodge buyer in that they expect more refinement from their Jeeps, and thus, upgrades and modifications were necessary to the engine.
The engine is the same basic supercharged 6.2-liter Hemi V-8 with the full 707 hp of previous Hellcats, and the supercharger still displaces 2.3-liters with 11.6 pounds of boost. It’s what you can’t see underneath the supercharger that’s been enhanced.
Modifications include reduced valve overlap and new cam timing, both to improve idle stability. The exhaust manifold is new with high nickel content and cast iron bits that allow it to handle temperatures as high as 1,740 degrees.
Many of the changes were to quiet the engine and make its sounds more refined. While the Grand Cherokee Trackhawk shares the Dodge Hellcat’s 92 mm throttle body, it has a unique air induction setup with its own air box design, a new air induction tube that modifies the sound of the supercharger whine, and a Helmholz resonator tuned by SRT engineers for this application. No other Hellcat will have a Helmholz resonator, which takes the peaks out of the low and high ends of the sound range, and allows the supercharger whine to build as you step into the throttle instead of being a constant companion.
The mufflers from the Durango SRT were used to achieve the exhaust note and specifically tuned for the Trackhawk.
Jeep had to confront another problem. How would it send 707 hp and 645 pound-feet of torque to all four wheels?
2018 Jeep Grand Cherokee TrackhawkEnlarge Photo
The Trackhawk is the only all-wheel-drive Hellcat, and that required strengthening the Grand Cherokee’s all-wheel-drive system to ensure it wouldn’t explode when dealing with big bursts of power.
The system features a new single-speed active transfer case with a limited-slip rear differential. Engineers had to shorten the transfer case length due to the size of the transmission, which was bolstered to handle up to 860 lb-ft of torque, and use a wider chain with forged steel sprockets that wouldn't break when subjected to a full-throttle launch. The differential has gone from a two-pinion to a four-pinion setup to improve torque capacity, and the casing went from a three- to four-point mount to spread the stress it endures. Even the ring and pinion setup has new tooth geometry to improve tooth bending strength (i.e. so it doesn’t break).
Packaging all this into the Grand Cherokee was no small feat, and the engineers said they were constrained in the rear end by the existing hub design. A new, stronger half-shaft was designed to fit in the current space, and a new 8-ball constant velocity shaft was created as well for increased durability.
Interestingly, the entire front axle and front driveshaft are carryover from the Grand Cherokee SRT, which has "just" 475 hp and 470 lb-ft of torque.
To show off the fruits of its labor, Jeep invited Motor Authority to Portland, Maine, to drive the Trackhawk on the street and track, and try out a few hard 0-60 mph launches for good measure. I drew the mission and was happy to accept it.