Nov 042013
 

The principle of evolution from apes to humans also applies to the biblical behemoth.

In one of the fictional books written prior to the creation of human beings, the apes penned that behemoths were rumor to roar the, was then, juvenile earth. Behemoth was a mix-breed beast between dinosaurs, crocodile, and a mythological creature, as if the experiment of human creation had gone awfully wrong upstairs.

Fortunately, evolution by means of natural selection prevailed. The higher intellectuals Newton, Einstein, Otto, Diesel, Wankel were mutated. The behemoth has also evolved and adopted by most American families. The specie is now referred to as Esuvee.

The fictional book that glorified the behemoth should be modified to the following:

Behold now the Esuvee that the higher intellectual have made with you; It drinks gas like fighter jet.

Behold now its strength is in its towing and its power is in the valley of the vee.

Its tail hitches a trailer with cedar flooring; the drawbar of its hitch is couple together.

Its limbs are as strong as stamped steel, its skeleton separates from its skin.

Its the first of GM’s ways; only its maker can draw its crowd.

For the mountains bear demand for it, and all the beasts of the field play there.

Does it lie under the shadows, in the cover of the reeds and the swamp?

Do the shadows cover it as its shadow? Does the standard garage surround him?

Behold, it fords the stream, and does not drown; it trusts that it will not draw water into his lung.

The subspecies we discuss here is the GMC Yukon.

Background – It’s the first of GM’s way; only its maker can draw its crowd.

The first generation of GMC Yukon was introduced to the market in 1992. The initial model was a 2-door version fitted with a 5.7L V8 that produced 200 hp and 310 lb-ft of torque. The Yukon shared GM’s GMT400 full-size body-on-frame truck chassis with the GMC Sierra. A more powerful, and efficient Vortec 5700 V8 was fitted in 1995. It generated 255 hp, and 335 lb-ft of torque from the same displacement, mated to either four-speed AT or 5-speed manual. A 4-door version was introduced in the later production.

The second generation was released to the market in 2000 on the new full-size truck chassis (GMT 800) and shared with the GMC Sierra. Both the manual, and 2-door version were dropped from the lineup. Two small-block V8s ranged from 4.8L to 5.3L were available. Since then the Yukon and the Chevrolet Tahoe had been the identical twin, and closely related to Cadillac Escalade.

In 2007, the third generation was introduced at the verge of the economy bubble. It’s high price, excessive fuel consumption, and resources spent in the development fueled the failure of General Motor. The 67% reduction in Yukon’s sales volume between the 2004, and 2010 was also the contributor.

The Yukon is available in SLE, SLT, and Denali trims along with a Hybrid model in 2012. The optional equipment matrix in domestic brew products are very complex, the Yukon is no exception. Simplistically, the only interesting packages are listed here. The optional Z71 Off-Road Suspension Package is available on 4WD SLT model. It includes skid plate, high-capacity air cleaner, and heavy-duty trailer with trailer brake controller.

The Denali trim is focused on luxury, and closely equipped as the Cadillac Escalade. The Denali comes standard with AutoRide suspension that consists of bi-state variable shock dampening, and rear air-assisted load-leveling. Inside it has heated and cooled perforated leather-appointed seats on the 12-way power front seats and heated steering wheel along with heated side mirrors with blind spot alert, and a power lift-gate.

All these luxury items push the Denali curb weight to 5,688 lbs. A 403hp and 417 lb-ft of torque Vortec 6.2L V-8 is fitted. The powertrain is capable to propel the Denali from 0-60 in 7.5s with fuel consumption MPG ratings at 13 city, and 18 highway.

Our Arlington, Texas assembled tester in Gold Mist Metallic paint is the, third generation, SLT 4WD model. Its $49,650 MSRP includes destination fee, and the optional fog lamps.

Impression – For mountains bear demand for it, and all the beasts of the play field there.

The Yukon is suitable for people who live high up in the Eastern Sierra where the terrain resembles the secluded Yukon, Canada. Living in the Sierra high desert with a family where weather, traveling distance to daily activities, to weekend entertainments like offroading, hot springing, camping, skiing, boating, and even the monthly grocery shopping at Bishop requires an ample, temperature regulated cabin that pick up will not do. These all support the need of a full-size truck based SUV.

To experience the Yukon style of living, and to fully explore the capabilities of our Yukon, we gathered a team of six souls, packed them on board with a trunkful of camping gears for a weekend getaway. We escaped from the crowded San Francisco to Yosemite. The 550 mile test route included Bay Area freeways, the winding US120 via the Old Priest Grade bypass route that goes from elevation 1065’ to 2,475’ with slope averaging at 14.5%.

Initial impression is that the Yukon is big to look at, and even bigger on the road. The behemoth genes indeed are still dominant in the Esuvee.

Powertrain Performance & Refinement – Behold now its strength is in its towing and its power is in the valley of the vee.

Situated under the chest height hood is a longitudinally mounted Vortec 5.3L small black V8 engine (engine code: LMG) sourced from the General Motor family. The LMG generates 320 hp @ 5,400 rpm, and 335 lb-ft of torque @ 4,000 rpm on regular unleaded; and increases to 326 hp & 348 lb-ft on E85 fuel.

In this towing and hauling, torque is king full-size big boy segment. The LMG’s torque output is somewhat shy when compare to the 2012 Dodge Durango R/T’s 390 lb-ft 5.7L HEMI V8.

The LMG was developed specifically for durability. Deep-skirt cast iron engine block where the walls of the block are extended below the crankshaft centerline. The deep-skirt creates a stiffer, box-in crankcase. The oil pan is integrated to the bottom-end structure to further enhance the block stiffness, and to minimize vibration. The bottom-end hosts six cross-bolted main bearing caps to secure the forces exerted by the connecting rods on the crankshaft. The forces are generated by the 96mm x 92mm bore-to-stroke oversquare layout with 9.9:1 compression ratio.

Each of the eight cylinders is breath through a 2” intake and a 1.55” exhaust valves. Casted into the aluminum alloy cylinder heads, the intake ports have straighten flow path from the composite intake manifold and features the traditional “cathedral” port design rather than the modern rectangular-port. The cathedral-ports offer better low-speed power and produces peak torque at lower rpm. The exhaust ports are shaped like letter “D”, turned 90-deg counter-clockwise. The idea is that the exhaust gas is naturally forced out of the exhaust valve traveling at the crown of the port. The D-ports improve exhaust flow by retaining its velocity.

A pair of cast nodular iron exhaust manifolds are mated to the D-ports to divert the gas and to promote scavenger effect by heat retention (the hotter the gas, the faster it flows). The manifolds are further covers by triple-layer heat shields to reduce underhood temperature. The exhaust is specially tuned to account for the second-order exhaust pulses during the V4 mode.

The V4 mode is GM’s Active Fuel Management (AFM) technology, formerly, Displacement-On-Demand. AFM temporarily deactivates four of the eight cylinders under light load conditions and reactivates them when power is in demand. AFM is enabled by utilizing the timing chain driven variable valve timing on the push-rod valvetrain. The centrally located camshaft makes the implementation of AFM simpler. Mechanically, the hydraulic controlled cam phaser is integrated at the cam gear sprocket, thus camshaft duration and timing can be adjusted to optimize performance and efficiency. The cylinder deactivation is achieved by closing both the intake and exhaust valves on cylinders 1, 4, 6, and 7 by electronically controlling the oil flow into the hydraulic lifters. The sequential fuel injection also shuts off the injectors serving these cylinders to improve fuel economy.

Controlling all of these, and the throttle input is a 32-bit, 59Mhz processor ECM with 32Mb of flash memory and 128Kb of RAM on high-speed CAN Bus. GM claims that the AFM transition takes less than 20 milliseconds, and is virtually indiscernible to most drivers. GM also claims that AFM increases fuel economy approximately 6 percent. However, the time spent in the V4 mode we observed was minimal.

On the road, undeniably, the engine has good low end torque, and revs smoothly to its 6,000 rpm redline. The engine note is too subtle for our liking. We now understand why most Yukon have an aftermarket exhaust system – a must for V8 symphony. Otherwise, the Yukon sounds too much like an Uhaul.

Mated to the backend of the longitudinally mounted engine is GM’s Hydra-Matric 6L80 six-speed automatic transmission that is also found in GM’s performance vehicles: Corvette, Camaro SS, and Pontiac G8.

Given the number of forward gears, 32-bit transmission control module, and performance proven applications, we would expect some snapping fast shifting actions. Wrong! There seems to be no urgency in getting into gear; perhaps, there’s no real time constraint in the Sierra desert. In exchange for the laziness, smooth shifting action is then anticipated. Wrong! The downshifts are jerky and eventful. The transmission behaves similar to the ones dated back to the early ‘90s. To make matter worse, the 4WD drivetrain has more than tolerable slack, it acts as if the U-joints, and driveaxles are worn. The slack is felt with each gear change.

Ignoring all that and pin the accelerator to the floor, this powertrain is capable of propelling the tester’s 5,567 lbs curb weight from 0 to 60 mph in 8.3 seconds, and reaches the quarter mile in 16.3 seconds at 84.2 mph while overcoming its 0.36 coefficient of drag (power to weight ratio of 17.4 lbs/hp, and 16.6 lbs/lb-ft). For the sake of comparison, the aforementioned Durango can go from 0-60 in 6.7s, and quarter mile in 14.9s at 90 mph.

Filling up the 26 gallon gas tank is bank breaking. One of the six souls who came from part of the global where gasoline worth like gold ($9 per gallon), and accustomed to efficient vehicles dropped his jaw, and mistakenly thought the Yukon has two fuel tanks when the Yukon sucked up more than $80 worth of fuel. Our observed average fuel consumption MPG was 16.2, which agreed with EPA’s 15 city, 21 highway, and 17 mpg combined ratings, and on par with the Durango’s 13/20/15.

  One Response to “2012 GMC Yukon SLT 4WD”

  1. She’s a beautiful beast. Take her to the track and beat her like a rented mule. Why not….

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