The Chevrolet Tahoe Hybrid has a base price of $50,490 for the two-wheel drive model and $53,295 for the four-wheel drive model. EPA city/highway fuel estimates are 21/20 mpg and 20/20 mpg respectively. This is a tale of two Tahoes. One is the poster child for excess, size and high mileage while the other Tahoe could be one of the saving graces for the segment.
Full-size SUV and pickup sales have tanked to the tune of approximately 42 percent based on recent industry figures. As we all know the sales slide is due primarily to high fuel costs.
The Tahoe Hybrid is not a quick knee-jerk reaction vehicle as GM, in partnership with BMW, Chrysler and Daimler have been developing the technology for several years prior to this current fuel crisis. Chrysler uses the same technology for their new Aspen and Durango full-size hybrids. GM also offers the system in the GMC Yukon and Cadillac Escalade.
While the Hybrid drive system could help save the full-size SUV segment, it can only do so much to help a heavy 5,840-pound vehicle. The Tahoe Hybrid 2WD achieves EPA city fuel economy of 21 mpg. This is a whopping 50 percent increase over the gas-only version and about equal to the city fuel economy of a four-cylinder 2008 Toyota Camry. The highway mileage comes in at 22 mpg.
This truck was also put on a diet to shed 350 pounds to compensate for the hybrid components. This “diet” consists of an aluminum hood, liftgate, front bumper support components and engine. Additional lightweight items include seats, wheels, a 12-volt battery and the deletion of the starter motor.
The Tahoe Hybrid's 6.0-liter, 332-horsepower V-8 is equipped with the GM Active Fuel Management system, which disengages half of the engine’s cylinders when full engine power is not needed. The system allows the engine to move seamlessly from V-8 to V-4 as driving demands.
Electric-only propulsion is available up to 30 mph, which is key to reducing fuel consumption in heavy stop-and-go traffic -- something all too common in our area. Electric power also assists the engine to save fuel during hard acceleration or when needed for additional pulling power for towing up to 6,000 pounds. During vehicle deceleration, fuel is actually cutoff to the motor and the hybrid system’s battery pack is recharged via regenerative (normal) braking. During emergency braking the conventional hydraulic braking system takes over to make sure the vehicle slows as completely as road conditions will permit.
The main component to GM’s all-new electrically variable transmission (EVT) is its unique combinations of two 60 kW electric motors, three planetary gear sets and four traditional hydraulic wet clutches. This setup allows continuously variable operation as well as provides four fixed gear ratios (with operation comparable to that of a standard electronically controlled automatic transmission). A sophisticated Hybrid Optimizing System constantly receives torque-based data from the powertrain and other vehicle systems, and then selects the most efficient manner of propelling the vehicle: electric power, gasoline engine power or a combination. The EVT has a dual personality -- continuously variable drive for light-load conditions and fixed-ratio drive for high-load situations.
GM terms these two EVT operations as “modes.” In Mode One (M1), the EVT provides infinitely variable drive up to 1.70:1. In Mode Two (M2), it provides ratios from 1.70:1 to 0.50:1. These two modes include all instances of electric-only (Auto Stop) and electric-gasoline hybrid operation. Depending on driving conditions and vehicle load, a fixed first-gear (G1) ratio of 3.69:1 is available (such as for pulling a large trailer) instead of the variable M1 ratios. A second-gear (G2) fixed ratio of 1.70:1 may be selected by the hybrid operation system, if needed, before transitioning to the variable M2 ratios. As road speed increases, and depending on driving and vehicle load conditions, variable-ratio M2 operation will switch instantly to a third-gear (G3) fixed ratio of 1.00:1 and finally to a fourth-gear (G4) fixed ratio of 0.73:1, which is employed for steady-state highway driving.
OK, the tech session is over.
So where does the juice come from? The power to the EVT’s two electric motors comes from a 300-volt nickel-metal hydride Energy Storage System (ESS). This battery pack is located under the second-row seats. The primary function of the ESS is to provide power (300 volts) to the EVT via the Traction Power Inverter Module (TPIM) and to store captured energy produced during regenerative braking. The ESS can also be charged, when necessary, by the gasoline engine via one of the two electric motors when operated in generator mode. In addition to supplying power to the EVT, the ESS also provides power to the air conditioning compressor and the Accessory Power Module (APM), which converts the high-voltage supply to 42 volts for the electric power steering system and 12 volts for the vehicle battery and other 12-volt electrical accessories.
As for battery pack longevity, GM warranties it for eight years or 100,000 miles. GM claims that durability and reliability are maintained via optimized charge and discharge cycles as well as a dedicated cooling system that draws air from the passenger compartment to keep things cool.
Eyeballing a standard Tahoe and a Hybrid version side by side, you’ll note little tweaks on the Hybrid version like a cowcatcher style front air dam, a rear spoiler, smoother front and rear fascias, molded running boards and D-pillar trim pieces all added to help manage airflow and cut drag.
Taking the Tahoe Hybrid out on the road is an odd experience at first. It feels like a super-sized golf cart. There just isn’t any meaningful or tangible connection to the road. The same holds true for the Tahoe’s electric power steering. The engine shuts off (very calmly and smoothly) at every full stop.
This brought back horrible flashbacks of my high school/college days when I drove very used and inexpensive “beaters” during the winter months while I stored my hotrods. Sometimes these cars quit in the middle of a busy intersection or on the highway, and I can tell you it’s a sensation that you never forget.
To waken the Tahoe, however, you just tap the accelerator, and the Tahoe silently hums along picking up speed. The transmission moves through the modes ghostlike without any noticeable shift points.
By feather-footing the accelerator and watching the gauges, I achieved some outstanding fuel mileage during the test period at just more than 22 mpg. This did include some continuous driving stretches. Aside from the engine shut downs, I never felt alarmed by the driving behavior, the maneuverability or acceleration of the vehicle. That said, the tradeoff is a very removed driving experience -- one that I can honestly say I did not like.
Additionally, I was not impressed with the sea of gray interior and the look/feel of the components in a vehicle that cost $52,780, including a $900 destination fee. The major options were a sunroof for $995 and a rear-seat entertainment system for $1,295.
As for fuel savings, it really depends on how much gas costs and how much stop-and-go driving (braking) you do. A comparably equipped 2WD Tahoe LTZ with a 5.3-liter V-8 stickers for $49,730, which includes destination; the up-charge for the Hybrid model works out to $3,050. A comparable 6.0-liter V-8 2WD Tahoe is not available; however a 6.2-liter V-8 with 12/19 mileage numbers is a $1,295 option.
The 5.3 Tahoe hauls in 14/20 mileage numbers, so if you drive 15,000 miles per year in stop and go/city driving you will save 357 gallons of gas. If gas averages $4.00 per gallon, you would save $1,428 per year on fuel. This translates into approximately 25-28 months to recoupe the added cost of the Hybrid model.
This is an oversimplification as there are a great deal of factors involved, chiefly that you to operate this vehicle in the city or for a lot of short stop/go trips to recapture the braking energy. The more highway cruising you do, the longer it will take to reach the breakeven point. Also, remember that you will have to replace the battery pack at some point in the future, or more than likely, take a hit on depreciation at trade-in time depending on how many years of warranty/life are left on the battery pack.
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