Hemi V8-powered Wrangler Rubicon 392 tested off-road

BACK in the day, and we are talking about the 1960s, Detroit was churning out high-output big-displacement V8s like burgers from a McDonalds’ drive-through.

But the energy crisis of the 1970s gave pause, and the added burden of the 80s’ emissions requirements choked the life blood out of any dreams of hot-rodding around with a HEMI behind a seven-slot grille.

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Yes, the Grand Cherokee made impressive strides with the SRT8, but it has been nearly four decades since a CJ-7 rolled out of Auburn Hills (Michigan) with the 5.0-litre (304cid) engine. But what about the Wrangler? It has led the brand for 35 years but has been relegated to V6 and I4 engines … until now.

ENTER THE RUBICON 392

We were near Moab, Utah, for the Easter Jeep Safari and I slowed down to 65km/h at the base of a long, paved, uphill grade. I pressed a funny little ‘goggles’ button on the dash and pinned the skinny pedal. Bam! My head whipped back against the headrest as I felt the Gs press my spine against the seat.

The throaty sweet notes of an uncorked exhaust echoed through the cockpit as the speedo spun north toward the century mark. We hit ‘V max’ in a heartbeat (the maximum tyre rating speed of 99mph or 159.3km/h) and I backed off the throttle to coast up to the crest.

Peeling off on a dirt track, my mind drifted back to high school days of HEMIs and Dodge Challengers and thought, “Damn, this is one badass Wrangler.”

GO V8 OR GO HOME

FOR years we’ve been asking Jeep to put a V8 in the Wrangler, and it is now evident they were listening. But they didn’t settle for a mere 5.7-litre, they went big, borrowing the proven 392cid (6.4-litre) HEMI from the SRT Grand Cherokee.

Retuning it for the dirt, this bad boy cranks out an adrenaline-inducing 470-470 … as in horsepower and torque respectively (350kW-637Nm). It is mated to a TorqueFlite eight-speed automatic transmission, with a Select-Trac transfer case distributing power fore and aft.

With all these cubes stuffed behind the grille, air flow and cooling are paramount. To accommodate this, the hood features a functional scoop that sends air into a ducting system called Hydro Guide. It directs flow to the air filter while vacating up to 60 litres of water per minute.

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If you’ve ever dunked your bonnet in a billabong or crossed a flooded creek where the bow wave rolled up to the windscreen, you will understand Hydro Guide’s utility.

Down below are a pair of Gen III Dana 44 axles fitted with electronically controlled Tru-Loc differentials and 3.73:1 gears. They are capped with twin-piston disc brakes borrowed from the Gladiator Mojave (345mm rear, 330mm front) and steering is the electro-hydraulic system introduced with the JL.

WATCH: Off-road in Jeep's SWB Wrangler Rubicon Recon

We’ve come to appreciate the Rubicon’s coil-linked suspension, but the 392’s has been revised to handle the increased power, torque and mass of the HEMI.

Front spring ratings were increased by 20 per cent while the rears were surprisingly reduced by 10 per cent, and specially tuned Fox aluminium shocks managing damping. Suspension links, track bars and cross members have been strengthened, and specific sections of the frame re-engineered.

EXTERIOR

WALKING around the 392, it looks like a basic four-door Rubicon, but the observant eye will notice subtle differences. It sits higher, two inches over the Sport and an inch over the Rubicon to accommodate the dimensions of the HEMI.

Grille slots are a bit wider to allow for increased air flow to the engine compartment, and an optional forward-facing camera rests in the middle.

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Armour includes Jeep Performance Parts (JPP) rock sliders and steel bumpers accented with bronze recovery points. Peeking under the rear bumper we find two tailpipes per side (more on this in a minute) and maintaining contact with the tractive surface are 33-inch BFGoodrich KO2 All-Terrains wrapped around Mopar’s new bead-lock-capable wheels. And, how could we miss the 392 badging on the hood.

INTERIOR

THE 392 might not have borrowed the interior directly from the Gladiator Mojave, but it sure took cues. Enhanced seat bolsters keep you securely tucked in place, lumbar support is prominent, and ergonomics have a sports-car feel … right down to the paddle shifters at a fingertip’s reach.

Bronze stitching, similar to the honeycomb on the grille, accents the leather-wrapped wheel and carries on throughout the interior. At arm’s reach is the 8.4-inch Uconnect screen, your portal to apps that monitor everything from HVAC and engine vitals, to drivetrain engagement and tilt angle. Scrolling through the options we find the forward-facing off-road camera, which provides a 180-degree view of upcoming terrain.

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Locker controls are in the normal spot in front of the transmission shifter, and allow one-touch engagement and disengagement.

What’s new is the Off-Road+ feature … and the curious button with a pair of goggles? You might recall Off-Road+ from our review of the Gladiator Mojave, but read on about this goggle thing – it will put an ear-to-ear smile on your mug.

MASH AND BEANS

AS you might surmise from the 392’s stats, if you mash the skinny pedal it’s got the beans to slap your head back in the seat, I kid you not! Zero to 60mph (96.5km/h) in 4.5 seconds and a 13-second quarter mile, this bad boy gets up and moves – and would beat the tailpipes off my old ’71 Challenger.

However, heaps of power is of little use if you don’t have a suspension to control it. How does it manage G-outs? Are the shocks tuned for high-frequency, low-amplitude input (corrugations)? Does it porpoise during hard braking? How does it manage tight cornering? What is its return-to-centre ratio? Is the suspension balanced?

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Before turning on to the dirt, I engaged Off-Road+. Pressing this lovely little button enhances throttle response, modifies transmission shift points, and detunes the Traction Control system. You can also permanently disengage electronic stability control (ESC), putting full control in the driver’s hands without an electronic nanny pulling the plug. It will also allow rear locker engagement in high range and at any speed.

After a day of blasting down two-tracks, through dune fields and crawling over technical terrain, I must say Jeep did an impressive job on the suspension. The combination of spring rates, damping and traction rendered predictable results during hard drifts.

Hitting a set of rollers carrying too much heat (one of those oh-crap moments) we cut through like a hot knife through butter, the shocks sucking up the bumps with impressive acumen. Damping, both compression and rebound, is critical in high-speed G-outs. Too little or too much and things can get messy.

The bottoms were firm, and rebound was controlled. Dropping in to a sand wash and pressing down on the happy pedal was pure joy. As for performance in the dunes, reread 470 ponies under the bonnet. Predictable, that is the operative word. A predictable suspension that builds confidence and trust.

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The 392 doesn’t have the Rubicon’s iconic 4:1 transfer case, and its low-speed crawl ratio of 48:1 doesn’t break any records. However, 637Nm makes up for a lot of gearing and we navigated some fairly technical terrain without issue – we were nowhere near the capability limits of this vehicle.

I will say I would have liked a bit more compression braking on steep declines – probably the only shortfall of the 2.72:1 transfer case gearing.

Now let’s get back to that curious pair of goggles on the dash. We’ll call this the ‘annoy your neighbour button’. One touch engages the Active Dual-Mode Exhaust, which has two settings: Normal is for when you don’t want to T-off the grandparents, the other is for those times that you want to relive your muscle car days.

The magic resides in a vacuum-operated solenoid that opens an internal gate in the muffler. This effectively uncorks the exhaust and releases the full fury of the 6.4-litre HEMI for the world to behold. Well, we enjoyed it.

THE WRAP

ALTHOUGH it has taken decades for Jeep to embrace our pleas for a V8 Wrangler, when they finally got around to it they did a bang-up job.

With the trail capability of a Rubicon, a high-output 6.4-litre mill under the bonnet and downright impressive handling, what is not to love about the Rubicon 392? Well maybe the fact that it is being built in left-hand drive only, so it’s another vehicle not for Australia ... c’mon Jeep, bring the Wrangler 392 Down Under!

SPECS

ENGINE: 6.4-litre HEMI V8
MAX POWER: 470hp (350kW) at 6000rpm
MAX TORQUE: 637Nm at 4300rpm
GEARBOX: 8HP75 TorqueFlite 8-speed auto
4X4 SYSTEM: MP3022 Select-Trac
CRAWL RATIO: 48:1
WHEEL/TYRE: 17x7.5in alloy/ LT285/70R17 BFGoodrich KO2 AT
KERB WEIGHT: 2314kg
TOWING CAPACITY: N/A
FUEL TANK CAPACITY: 81.3lt
PRICE: USD$73,500
DEPARTURE ANGLE 37.5⁰
RAMPOVER ANGLE 22.6⁰
APPROACH ANGLE 44.5⁰
WADING DEPTH 825.5mm
GROUND CLEARANCE 261.6mm

WATCH: The Wrangler Rubicon 392 in action