GMC Yukon Hybrid: Better Living Through Technology

It starts with a jolt; the result of a simple twist of the wrist. Six litre’s worth of exploding petroleum product echoes down the exhaust with a hearty burbling bass line as the massive momentum of the V8’s rotating assembly carries itself through the motor mounts, carrying up into the seat bottoms. But all this leaves one to wonder; is there anything substantial behind the much-lauded 2-Mode Hybrid system that’s proudly advertised on this, and so many other GM product flanks?

And then, just as easily as it started, it stops. The tachometer drops to zero, the reverberation of the V8 ceases, and that familiar burbling exhaust is abruptly silenced. Working the column shifter through the gates until the selector gates identifies the letter D on the dashboard, the Yukon slides away from the curb with a slight mixture of an electric motor’s whir and high-voltage whine. Being conservative with the gas pedal, the Yukon will continue on electric power alone, reaching a hair below 50 kilometres per hour before a slight shimmy felt through the seat bottom signals the re-ignition of the V8 powerplant.

• Also: GMC Yukon Hybrid: Best of both modes, best of both worlds!
• Also: 2009 Chrysler Aspen Hybrid: The Best Vehicle You Didn't Know About.

However, while the Hybrid system’s operation seems overly simplistic from the driver’s seat, the reality is that it’s anything but. At the heart of the new 2-Mode hybrid drive system; GM’s appropriately named Electrically Variable Transmission. Incorporating two 60 kW motors (the combined output of which is roughly 160 horsepower) and four hydraulic clutch packs, the transmission harnesses the power supplied by the 300 volt nickel metal hydride battery pack to propel the Yukon on gasoline power, electric power, or any combination of the two. But where the Yukon differs from traditional hybrid vehicles is in the two-mode operation of the transmission. By virtue of its SUV nature, the Yukon demands the durability of a fixed ratio transmission, while the electric motors require the variability of a CVT (continuously variable transmission). The result is the two-mode transmission that can operate in either manner, with Mode One providing an infinitely variable gear ratio up to 1.70:1, while Mode Two provides ratios from 1.70 to 0.50:1. Under heavy load, or steady state highway cruising, the transmission utilizes a traditional four speed gear spread, with fourth being a 0.73:1 overdrive. At highway speeds, the Yukon is most efficient when running off the gasoline V8 alone; the combination of its vastly redesigned aerodynamics and GM’s active fuel management system that selectively deactivates cylinders depending on the engine’s load. Oftentimes, while traversing the local highways at between 90 and 100 kilometres per hour, the Yukon Hybrid’s fuel economy display generally indicated four –cylinder operation, while hills and passing manoeuvres would call all eight cylinders and the electric motors into service to smash the Yukon’s 5,835 pounds through the air.

Inside, the Yukon Hybrid’s simulation of a standard Yukon continues. The same cosseting, wide seats are present in all seven seating positions, and the same adjustable and commanding seating position grants fantastic vision for the driver, with massive expanses of glass giving passengers a nearly unobstructed view of the passing scenery and greenery. While a lot of the switchgear will be familiar to GM owners, the planning and execution of the Yukon’s interior is delightful, with easy to use controls, good panel gaps, and luxurious materials. That said, with a swath of faux wood panelling flanking the center console’s faux brushed steel trim, one can’t help but wonder why GM can’t conjure up a supplier that could provide them with slightly more believable faux finishes. The finish of the fake wood is dimpled and yet glossy and purely plastic, while the faux brushed steel trim is far too glossy to be believed. From the driver’s seat, there’s just two indications as to the technological tour de force that sits under the hood; the completely useless “eco” gauge, and the Auto-Stop position on the tachometer. Supposedly evaluating the driver’s fuel efficiency, the eco gauge has no indication as to which way is good, and barely moves except during braking, when it dips to the left to signal the operation of the regenerative brakes siphoning power from the brake calipers and pumping it into the aforementioned 300 volt battery pack. Themselves an artful deception, the regenerative brakes are of course backed by a traditional hydraulic brake system; the combination of which provides the Hybrid with far more stopping power than the gasoline-powered models, which equates to shorter stopping distances. During regenerative braking operation, the Yukon uses a brake pedal emulator to increase brake pedal effort as it is depressed to provide a brake pedal feel that is indistinguishable from traditional hydraulic brakes. The only intrusion is the occasional noise of the hydraulic brake pedal accumulator pump that maintains hydraulic pressure in the braking system. As was discovered, repeated brake pedal depression will deplete pressure faster and cause the pump to cycle more often... or it should have. For some reason, the test vehicle’s pump failed to cycle in a Burger King drive through; igniting three dashboard trouble lights and causing a severe increase in the amount of effort it took to stop the vehicle. However, simply shutting the engine off and restarting the vehicle cured the problem, which never occurred again.

Overall, the Yukon Hybrid does a nearly perfect emulation of the standard Yukon; and that’s a good thing. But, as expected, the Hybrid model is more fuel efficient... surprisingly so, in fact. During testing, the Yukon Hybrid recorded an average fuel consumption of just 12.2 litres per hundred kilometres. Compared to the 16.7 litres per hundred I encountered while testing its gasoline-powered brethren, the 2-Mode Hybrid system in the Yukon has the largest impact on fuel economy of any Hybrid vehicle I’ve operated. As compared to Toyota and Honda’s systems, the GM hybrid drivetrain protrudes less in the driving experience, and provides better fuel economy without affecting the Yukon’s SUV capability. But, all this technology does come with a price. Carrying a massive mark up of over $20,000 beyond the entry level Yukon’s price of admission, the Hybrid starts at just over $2,000 less than the ultra-luxurious Denali model, but forgoes that model’s bling-factor and some interior accoutrements. Is it worth it? Well that depends on you.