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Update: GM Law Enforcement Product Council

Earl Gautsche, GM Fleet national service manager, kicked off the Spring 2008 Law Enforcement Product Council (LEPC) meeting with a service update for the Impala and Tahoe. Both these police vehicles are actually free from significant, recurring service problems. However, all vehicles of all types have minor or intermittent problems.

Premature front brake pad wear may be an issue on the new generation 2006-2008 Impala. Braking performance remains excellent, but the front pads may need replacement in less than 8,000 miles, in some cases just 4,000 miles. GM Fleet is currently testing a Federal Mogul pad, and the issue remains under active investigation. In the time being, GM recommends continued use of OEM brake pads.

Premature rear tire wear on some hard-driven 2007-2008 Impalas has been traced to the rear toe-in. The Impala requires a 4-wheel alignment, and wear on the inside edge of the tread is usually a sign of camber problems. In some cases, the inside tread on the rear tires wears past the wear bars in as little as 7,000 miles. This has been traced to a soft durometer bushing in one of the rear suspension links. The soft-bushed lateral link allows a lot of tire squirm during aggressive driving. The solution, a harder durometer rubber bushing, went into production on all Impalas produced after March 2008. The GM reference document is #2074205.

Accelerated tire wear may also be an issue on the new generation 2007-2008 Tahoe. Instead of the expected 30K miles from the 17-inch Goodyear Eagle RS-A tires, some fleets are reporting just 10K miles. This issue is under investigation, and the findings will be reported at the Police Fleet Expo in August.

Some of the Tahoe 5.3L engines are experiencing a misfire at idle. In some cases, this has been traced to an intake valve hanging up in the valve guide. This occurs on the valves associated with the Active Fuel Management (cylinder deactivation) lifters. In these cases, the lobe of the camshaft has accelerated wear. The solution is to change the lifters and cam. More information is forthcoming.

Green Fleets

Every major car company in the world is developing less-gas and non-gas “green” vehicles. Connie Scarpelli, market and product manager, Passenger Cars outlined GM’s effort and introduced the four ride-and-drive vehicles.

The GM multi-pronged approach includes an increase in fuel efficiency through variable valve timing, cylinder deactivation, 6-speed transmissions and direct injection. The use of bio-fuels like E85 ethanol and B5 bio-diesel is viewed as just a stepping stone. All GM diesels are B5-capable, and soon will be B20-capable. Many GM vehicles are E85 FlexFuel, including both the police Impala and the police Tahoe.

GM is also using two different hybrid strategies, 2-Mode (full) Hybrid and BAS (mild) Hybrid. Earlier versions of the Silverado truck had the mild hybrid. For 2009, this truck will be upgraded to the full hybrid.

GM is also working on two kinds of electric vehicles. One is the gasoline-extended range electric vehicle, like the Chevy Volt. These cars use electric batteries capable of a 40-mile range on a single plug-in charge. The powertrain also includes a very small (1.0L turbocharged, 3-cylinder) gasoline engine to drive a generator that recharges the batteries, thus increasing the range to over 600 miles. Expect the Volt to hit showrooms in the 2010-2011 timeframe.

As GM moves from gas-friendly to gas-free, the ultimate step is the hydrogen fuel cell, the real long-term solution. The hydrogen fuel cell uses zero petroleum, produces zero harmful emissions and is close to a production reality. In fact, 100 Equinox Fuel Cell vehicles are in use by the postal service in Washington, DC. And “Project Driveway” has another 100 of these vehicles in the hands of regular vehicle owners in southern California, New York City and Washington, DC. This is the first, large-scale market test of hydrogen fuel cell vehicles using real drivers in the real world.

New for 2009

For 2009, GM Fleet has released its 1WT Work Truck Package, the commercial truck package, for the Chevy Silverado 2500 HD Crew Cab. This is an answer to fleets looking for the lowest cost truck in this range. This ¾-ton pickup does not have any police-specific equipment, i.e., it is not a police package and not a special service package. It is certainly not pursuit-capable. The 1WT Silverado comes with 4WD standard and is available with either the 6.0L gas V-8 or 6.6L diesel V-8.

The 2009 9CI police Impala, the 9C3 undercover Impala, the PPV police Tahoe 2WD and the 5W4 special service Tahoe 4x4 are all virtual carryovers from the 2008 models. Both the Tahoe and Impala packages will have the side-curtain airbags standard starting in the 2009 model year. And these safety items will not be able to be deleted under any circumstances. The 2009 Impala will also have seat-mounted (thorax) side airbags as standard equipment. The 2009 police Impala is not available with either Traction Control or StabiliTrak (electronic stability control).

For the 2009 Impala, Active Fuel Management (cylinder deactivation) has been deleted from the 3.9L V-6 engine. It simply did not produce the expected increase in fuel economy, and in patrol use, the 3-cylinder mode was almost never engaged. AFM kicks in under coasting but does not shut off cylinder during idling.

New for 2009, the Tahoe will get radial-drilled (not cross-drilled) front brake rotors. This venting is intended to help cool the brakes. In a related move, a heat shield will be added to protect the ABS cable near the rotors. The 2009 special service Tahoe 4x4 gets upgraded to a 6-speed transmission. The 3.73 rear axle ratio has been lowered to 3.42:1 to further improve mileage. The PPV police Tahoe 2WD remains with the 4-speed trans. GM has no plans for StabiliTrak on either the 2WD police package or 4x4 special service package Tahoe.


From an overall fleet view, GM offers two mild hybrid sedans, a mild hybrid SUV, four full hybrid SUVs and two full hybrid trucks. The company also has 23 E85 FlexFuel sedans, SUVs, trucks and vans. Both the police Impala and the police Tahoe are E85 FlexFuel.

The ride-and-drive portion of the LEPC meeting was “all green.” The cars included the Tahoe 2-Mode Hybrid, the Malibu BAS Hybrid, Saturn Aura BAS Hybrid and the Equinox Fuel Cell (all-hydrogen) crossover. GM Fleet does not have any plans for a police package or special service vehicle using a hybrid drivetrain, but the general topic is under study.

In GM-speak, the term “2-mode” means full hybrid, i.e., the gasoline engine shuts off while coasting and at idle, and the electric battery alone may power the vehicle up to 25 mph, depending on demand. The battery may also join the gas engine at higher speeds, depending on demand, engine rpm and gear selection.

The term “BAS” means belt alternator starter, which is a mild hybrid. The gas engine shuts off while coasting and at idle, but it starts up again to launch the vehicle from a stop. Under heavy demand, the same serpentine belt used to crank the engine to start may also be used by the battery to assist in turning the engine as it accelerates. This is a tiny step up from the simple start-stop hybrids of the past.

The star of the ride-and-drive was the pre-production, hydrogen fuel cell Equinox crossover. These vehicles drive exactly like they were powered by a gasoline engine. If you didn’t know you were in a hydrogen fuel cell vehicle, you would not be able to tell by any aspect of drivability. The smooth-running Equinox Fuel Cell has a 150- to 200-mile driving range. The 330-volt (125 hp-equivalent) system pushes the Equinox to 60 mph in 10.5 seconds and has a top speed of 120 mph.

Hydrogen Fuel Cell

Like all battery-powered vehicles, fuel cell vehicles are propelled by an electric motor. Both batteries and fuel cells produce electricity from a chemical reaction. In both cases, the fuel on the anode side and the oxidant on the cathode side react in the presence of an electrolyte. The big difference is that the fuel cell consumes the fuel, which must be replenished. Batteries, however, are closed systems, and you don’t add back anything to a battery in normal operation. The fuel cell uses hydrogen as a fuel and oxygen as an oxidant.

On the anode side, hydrogen diffuses into the catalyst, which it breaks down into protons and electrons. The protons pass through a membrane on the cathode side. However, the electrons are forced to travel through an external circuit, a flow that literally makes electricity. (Electricity is defined as the flow of electrons.)

On the cathode side, oxygen molecules (from the air or on-board supply) react with the protons and the electrons (from the external circuit) to form water. The only waste product from a hydrogen fuel cell is water vapor.

A typical fuel cell produces 0.7 volts, so fuel cells are stacked together and combined in both series circuits and parallel circuits. As a result, these fuel cell stacks produce both more voltage (series) and current (parallel).

First developed in the mid-1800s, the fuel cell has taken a long time to reach the streets as a power source. The first such vehicle was in 1966, the GM Electrovan, which reached speeds of 70 mph. Managing the heat produced by the fuel cell, finding an alternative to platinum in the fuel cell and establishing a safe and widespread hydrogen refueling infrastructure are all major technology challenges, but none are show-stoppers.

What was gee-whiz technology in NASA’s Gemini space project will be in mass production passenger cars, depending on automaker, between the 2010 and 2012 model years. With fleet vehicles lasting about five years, hydrogen will probably be an option for some tasks when you replace some of the vehicles you are buying today. If you are a muni fleet manager for more than just police sedans, at least some support and admin vehicles using fuel cells are in your immediate future.

For more info, check out the DoE’s Energy Efficiency and Renewable Energy Web site, Hydrogen can be produced from methane in natural gas, by electrolysis to split water into hydrogen and oxygen and by gasification of coal.

Published in Law and Order, Aug 2008

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