2005 Jeep Grand Cherokee SRT-8
A Jeep that does 0-60 in under five seconds...
Powered by a 6.1-liter HEMI producing 415 horsepower (85 more horses and 25 percent more power than the 5.7-liter HEMI-equipped 2006 Jeep Grand Cherokee) and 410 lb.-ft. of torque, the 2006 Jeep Grand Cherokee SRT8’s performance numbers included 0-60 mph in under 5 seconds, 0-100-0 mph in the low 19-second range, and 60-0 mph braking distance of approximately 125 feet.
“When we set out to create the first Jeep-branded SRT vehicle, the 2006 Jeep Grand Cherokee presented us with an incredibly capable starting point,” said Dan Knott, Director – Street and Racing Technology, Chrysler Group. “With an infusion of SRT DNA, the 2006 Jeep Grand Cherokee SRT8 is the new benchmark performance SUV. It has the raw power to outperform the Porsche Cayenne Turbo, while providing exceptional ride and handling, world-class braking, race-inspired interior appointments and functional, performance-oriented exterior enhancements.”
To create the first SRT vehicle with full-time four-wheel drive, SRT engineers developed a drive system that was lightweight, yet robust and reliable enough to handle massive amounts of horsepower and torque from the 2006 Jeep Grand Cherokee SRT8’s powertrain. One part of the equation was to create a new transfer case, combining housing components from two existing units with the upgrades needed to make it SRT-capable.
SRT engineers opted to use the front half of a Jeep transfer case chosen for its capability and light weight. It was mated to the rear half of a heavier-duty case, chosen for its ruggedness and ability to house the electronic full-time four-wheel drive system components. The transfer case output shaft was upgraded to handle high torque generated by the SRT 6.1-liter HEMI. The result was the 2006 Jeep Grand Cherokee SRT8’s unique transfer case, which provided the necessary power-handling capabilities for the Grand Cherokee SRT8 while weighing 60 pounds less than a Jeep heavy-duty case.
Under normal driving conditions, from 5 percent to 10 percent of torque was directed to the front wheels, but as much of the 6.1-liter HEMI’s torque as needed could be directed forward when additional traction or stability was required. Remaining torque was sent via a heavy-duty driveshaft designed for the European Jeep Grand Cherokee diesel model, to a Dana 44 rear differential upgraded with a larger ring gear within a new axle housing.
“We wanted the acceleration that only four-wheel-drive can provide,” said Knott. “Our goal for the 2006 Jeep Grand Cherokee SRT8 was to have a well-balanced vehicle with a high fun-to-drive quotient. The SRT-developed electronic four-wheel drive system is perfectly suited to this.”
Jeep Grand Cherokee SRT8 Powertrain
Providing horsepower and torque to the unique SRT four-wheel drive system was a specially tuned version of the new 6.1-liter SRT HEMI engine. Inspired by the original family of HEMIs, the SRT 6.1-liter HEMI employed the namesake hemispherical combustion chambers that provided power and efficiency, while retaining classic HEMI visual cues including the orange-painted cylinder block and black valve covers.
For more displacement, SRT engineers bored out the diameter of the cylinders in the HEMI by 3.5 millimeters each in order to increase the total displacement to 6.1 liters from 5.7 liters. Compression ratio was also increased to 10.3:1 from 9.6:1, increasing engine efficiency and power.
Engine breathing was increased with new higher-flow cylinder heads, a specially designed intake manifold and fresh-air induction system (which allows water-fording capability of up to 19 inches), and exhaust headers with individual tubes encased in a stainless steel shell. All were unique to the 6.1-liter HEMI engine. Larger-diameter valves and reshaped ports in the heads allow for maximized air flow. The intake manifold was designed with larger-diameter and shorter runners for higher-speed tuning. Exhaust was routed through a large-diameter (2.75-inch vs. 2.5-inch) exhaust system with 4-inch chrome tips.
To further increase horsepower, performance-oriented camshaft profiles were developed to allow more air in and out of the cylinders, as well as manage a higher engine speed. SRT engineers increased the HEMI’s peak power output engine speed nearly 20 percent to 6,000 revolutions per minute (rpm) from 5,000 rpm. Intake and exhaust valve stems were hollow, and the exhaust valve stems were filled with sodium to help dissipate heat more efficiently.
The high-performance SRT 6.1-liter HEMI was strengthened with redesigned components, including a reinforced engine block, forged steel crankshaft, high-strength powdered-metal connecting rods, floating-pin pistons (cooled by oil squirters), and an oil pan modified to manage oil return to the pan sump at high engine speeds.
Power from the SRT 6.1-liter HEMI was sent through a special torque converter to an SRT-upgraded A580 five-speed automatic transmission.
Jeep Grand Cherokee SRT-8 Ride and Handling
Chassis setup was aimed at balanced performance with SRT-tuned dampers, unique sway bars and specially tailored spring rates and suspension bushings. New front suspension knuckles featured a camber angle calibrated for optimum suspension performance. The ride height of the 2006 Jeep Grand Cherokee SRT8 was one inch lower than the Jeep Grand Cherokee, which lowered aerodynamic drag and contributed to the vehicle’s aggressive stance. To meet or exceed handling and safety criteria, the Electronic Stability Program (ESP) was specially calibrated for the 2006 Jeep Grand Cherokee SRT8.
Further contributing to its aggressive stance, the all-new 2006 Jeep Grand Cherokee SRT8 was fitted with unique forged 20-inch five-spoke aluminum wheels shod with high-performance Goodyear W-rated four-season tires with run-flat capability. Tire dimensions were 255/45/20 in the front, and a massive 285/40/20 in the rear.
With an optional hitch package available from Mopar, the 2006 Jeep Grand Cherokee SRT8 was capable of towing up to 3,500 pounds.
Grand Cherokee SRT-8 Braking
The braking system of the 2006 Jeep Grand Cherokee SRT8 was designed to provide outstanding capability as a counterpoint to the vehicle’s awesome launch and acceleration. All four wheels featured four-piston performance brake calipers developed by Brembo, finished in gloss black. Under braking, these calipers clamped down on 360 x 32mm vented rotors up front, with 350 x 28mm vented rotors in the rear.
A new front fascia made use of aero improvements to reduce lift and drag, while providing sufficient air flow to cool the 6.1-liter HEMI engine. The front fascia also helped increase brake-system cooling through integrated air ducts. In the rear, an all-new fascia incorporated an aggressive center cutout to accommodate dual 4-inch exhaust tips.
Another functional enhancement was sill extensions to help create downforce. The roof rack available on the Jeep Grand Cherokee was not available on the 2006 Jeep Grand Cherokee SRT8.
Three exterior colors were available: Bright Silver, Brilliant Black and Inferno Red. The interior was medium slate.
Power-adjustable, deeply sculpted performance seats in the front held occupants during aggressive maneuvering. Interior accents included a “carbon-fiber” technical finish on the leather-wrapped steering wheel, instrument-panel brow and shift knob, complemented by a “refined aluminum” finishing on the center stack, shifter and door-switch bezels.
Full instrumentation included a 180-mph (300 kph) speedometer, tachometer and temperature gauges, all trimmed with a unique blue accent and located within a carbon fiber-trimmed binnacle. Oil pressure and temperature may be monitored through a specially configured display unit centrally located in the instrument panel.
The 2006 Jeep Grand Cherokee SRT8 was assembled at Jefferson North Assembly Plant in Detroit, Michigan.