A Review of the 2006 GMC Sierra Hybrid Truck June 2005

When I pulled up to a stop sign in a GMC Sierra SLE full-size pickup truck recently, I noticed two things: It got very silent and still in the cab and the tachometer needle was resting on its peg. The engine had stopped.

But I didn't have to reach for the key to refire the big V-8, I just moved my foot from the brake and began to depress the gas pedal. The motor smoothly restarted and the vehicle began to move.

What's up with that? Well, it was the new 2006 hybrid version of the Sierra and that's the trick it performs to improve mileage.

The process isn't entirely seamless. If you're paying close attention, you can detect the engine restarting, but drive it around town for a while and the process becomes virtually unnoticed.

Only if you are very quick to move from brake pedal to accelerator will you detect a very slight hesitation, and as throttle tip-in is quite abrupt you'll also likely spin the tires of this two-wheel-drive truck.

In the not-too-distant past, big pickup trucks were based on the automotive equivalent of Stone Age technology and up until a decade or so ago had evolved only to, say, maybe the Iron Age. They were pretty basic vehicles that didn't need to change much to fulfill their roles on the worksite or farm.

Since the early 1990s, the breed has benefited from a little new millennium science. The Sierra Hybrid, however, takes the sophistication level of the pickup to a new level. And the rewards are fuel economy improved by perhaps 10 to 12 per cent and, consequently, lower CO{-2} emissions.

Tom O'Dell, technology planning manager at GM of Canada, says the Sierra and Chevrolet Silverado Hybrid are in the forefront of a three-part strategy designed to meet future energy and emissions requirements.

The first step is optimizing vehicles powered by internal combustion engines. "For the foreseeable future, these will represent the largest component of the vehicle fleet and savings there are critical," he says.

He points to such things as displacement-on-demand engines and E-85 capable vehicles that can run on up to 85 per cent methanol as examples. I drove a demonstration version of an E-85 Yukon recently and it works fine, but as the fuel isn't readily available in Canada it's not relevant here yet.

Step 2 will be the move into hybrid technology with vehicles such as the Sienna/Silverado, which will be followed soon by a hybrid Saturn Vue SUV and Malibu sedan. Full-size Tahoe and Yukon hybrids will arrive by 2007.

GM sees these as interim measures leading to a long-term future that will be powered by hydrogen fuel-cell technology, O'Dell says.

The Sierra is what is known as a mild hybrid in that its electrical system doesn't actually provide added power to propel the vehicle.

The hybrid system in the Sierra includes a control module that converts and controls 14-volt and 42-volt electricity provided by the engine-driven starter/generator and through a regenerative braking system. A large and heavy 42-volt lead-acid battery pack is stored under the rear seat.

The starter/generator replaces the normal starter and alternator and is integrated into the engine flywheel and transmission torque converter. An electro-hydraulic power-assist system allows the steering and brakes to function while the engine is turned off. Other electrical systems in the vehicle also continue to work when the engine is off. There are also four 120-volt, 20-amp outlets in the bed and cab, so the truck can act as a generator to provide power for tools or equipment.

The test vehicle, hybrid bits aside, was an SLE Extended Cab Standard Box 2WD version that lists for $34,910. The Hybrid package adds $6,900 to that and includes the Vortec 5300 V-8 (295 hp at 5,200 rpm/335 lb-ft of torque at 4,000 rpm) with four-speed automatic.

You also get dual-zone climate control, reclining front buckets (power on the driver's side), upgraded audio system, 16-inch alloy wheels and a heavy-duty suspension. Two-tone paint, delivery etc. brought the total to $43,310.

This is a very pleasant truck. It's big, which makes parking and tight quarters manoeuvring a bit awkward, and the ride is pretty hard, but it's comfortable, quiet, nicely appointed inside and it handles and goes well. The two rear-opening half-doors allow access to a rear compartment with a shaped bench that can hold three.

O'Dell says the hybrid version retains all the basic vehicle's ruggedness with the only downsides related to the weight of the hybrid system itself. In our 2WD truck, this reduced the towing rating by 136 kg and the payload by 219 kg.

What about fuel savings? According to the Canadian government's EnerGuide, a standard 5.3-litre Sierra is rated at 15.0 litres/100 km in the city and 10.6 on the highway. The Hybrid cuts this to 13.2 city and 10.4 highway.

In cost terms, EnerGuide says the regular truck will require the average owner to pay $1,794 for gas annually while the Hybrid will cost $1,642. At that rate, payback is obviously going to take a while.

So why would you buy one? Beats me, which may be why GM is only looking at about 300 sales this year. But then this whole process of switching over to more efficient vehicles has to start somewhere, doesn't it?

SOURCE: Globe and Mail

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