|
|
For Release: August 1, 2000
The Most Powerful Pickup Engines Drive Silverado and Sierra to New Performance Heights
DETROIT - Led by the most powerful lineup of gasoline and diesel engines in their class, the new heavy-duty Chevrolet Silverado and GMC Sierra powertrains provide superior performance and high fuel efficiency for any customer needs.
“Our new powertrain lineup includes the most powerful gas and diesel engines ever offered in these segments. They provide better off-line launch, the fastest acceleration and highest heavy pickup trailering and hauling capabilities,” said Tom Stephens, GM Vice President and Group Director of the Pontiac Vehicle Engineering Center.
“They’re also more fuel-efficient, have longer-lasting 200,000-mile (322,000-km) durability and more low-maintenance features than previous generation models. From virtually any perspective, they allow customers to do more and do it more efficiently.”
Duramax 6600 Diesel Provides Whole New Performance Level
The Duramax 6600 (LB7), replacing the 6.5-liter turbo diesel, is a 90-degree, injection, overhead valve (OHV), four-valve-per-cylinder turbocharged V8, with aluminum high-swirl cylinder heads and major cooling benefits. Developed through a joint venture (DMAX Ltd.) between GM and Isuzu Motors, it is produced at a brand new manufacturing facility in Moraine, Ohio.
The bottom line on the all-new Duramax 6600 Diesel says it all: the most powerful diesel ever offered in a heavy-duty pickup, with better economy (than the 6.5-liter), long-life 200,000-mile (322,000-km) durability and a compact, light weight design – it’s ideal for any heavy-duty application – commercial or recreational.
| Horsepower Torque |
| Manufacturer – Engine |
hp@ rpm |
lb.-ft.@ rpm |
| DMAX – Duramax 6600 |
300 @ 3100 |
520 @ 1800 (705 Nm) |
| Ford – 7.3L V8 diesel |
235 @ 2700 |
500 @ 1600 (678 Nm) |
| Dodge – 5.9L 6-cylinder diesel |
230 @ 2700 |
450 @ 1600 (610 Nm) |
Superior horsepower and torque provide many benefits. They include better off-line launch, provided by a 14 percent increase (over the 6.5 liter) in the Duramax 6600’s low-speed torque and best-in-class acceleration.
In fact, as the following comparison of automatic transmission-equipped models at the same weight level shows, the bigger the load that a Duramax-equipped Silverado or Sierra carries or the heavier the trailer it tows – the more rapidly it outdistances its competitors:
|
0-60 (sec.) |
30-70 (sec.) |
¼-mile (sec.) |
Speed (mph) in ¼-mile |
| At an 11,400-lb. GVW load level |
|
|
|
|
| Duramax 6600 with 3.73 axle ratio |
14.2 |
14.5 |
20.1 |
72.4 |
| Ford 7.3L with 3.73 axle ratio |
15.8 |
16.8 |
20.9 |
69.4 |
| Dodge 5.9L with 4.10 axle ratio |
19.4 |
22.1 |
22.3 |
64.1 |
|
|
|
|
|
| At the 22,000-lb GCW level |
|
|
|
|
| Duramax 6600 with 3.73 axle ratio |
25.8 |
26.9 |
24.8 |
58.9 |
| Ford 7.3L with 3.73 axle ratio |
29.9 |
33.5 |
26.0 |
55.9 |
| Dodge 5.9L with 4.10 axle ratio |
38.5 |
50.7 |
28.1 |
51.8 |
Aided by its light, 836-pound (379 kg) weight when fully trimmed, state-of-the-art Bosch injection and high pressure, common rail fuel system, the Duramax 6600 has 19 percent better specific fuel economy than the 6.5-liter. GM engineers also expect it to be more efficient than Ford’s 7.3-liter diesel V8 and Dodge’s 5.9-liter six-cylinder diesel.
With 300 hp/379 kg weight, the Duramax 6600 delivers a best-in-class 0.79 power-to-weight ratio, topping Ford’s 0.56 ratio (235 hp/422 kg) and Dodge’s 0.54 ratio (235/437 kg).
The Duramax 6600 is also amazingly quiet. At 32º F (0º C), for example, it has a cold-idle start-up noise of only 78 decibels (dBA). Basically, that’s half the (85.5 dBA) noise level of its next-quietest competitor, the Ford 7.3-liter. (Dodge’s 5.9-liter diesel is even louder.)
The Duramax 6600’s low noise, vibration and harshness (NVH) stem from the structural rigidity of its deep-skirt block design, its side-bolted main bearing caps, single-piece aluminum crankcase and full bell housing. The widespread use of isolating gaskets, coupled with laminated heat shields a laminated oil pan and cast aluminum valve covers further isolate noise. And pilot injection technology carefully pulses the fuel for extra quiet start-ups.
Features such as its induction-hardened cylinder bores, a nitrided forged steel crankshaft, sintered steel valve seats, fractured connecting rods and a single, in-block camshaft with roller followers (gear-driven), contribute to its 200,000-mile (322,000-km) durability. The engine was rigorously tested nearly twice as many (2,500) hours as normal – from idle to wide-open throttle and peak torque to peak horsepower – to validate its extraordinary durability.
Its highly robust cooling system includes: charge-air cooling, which enhances power while lowering internal operating temperature; a larger (than the 6.5-liter) 21-inch (533-mm) fan, with a lightweight composite construction; dual, high-flow thermostats; an integral oil cooler; an integral gear-driven water pump and oil spray piston cooling. Small jets near the bottom of the cylinder walls spray cooling oil precisely through a hole in the piston skirt, as the piston moves up and down, rather than in the largely random fashion of other high capacity diesels.
The Duramax 6600’s high, flat torque curve delivers close to 90 percent of its power across the power band for superior launch and low-end pulling power, quick acceleration and best-in-class heavy-duty trailering/ hauling capability. The truck provides a maximum gross vehicle weight rating (GVW) of 12,000-pounds (5,443 kgs) and Gross Combined Weight Rating (GCWR) of 22,000-pounds (9,979 kgs).
Vortec 8100 Big Block V8 Outpowers Competitor’s V10s
The Vortec 8100 (L18) is essentially a new engine. Nearly 80 percent of its parts have been redesigned. Yet, its foundation is one of the most celebrated engine components in automotive history, GM’s Big Block V8. The Big Block even competes against diesels in highly demanding marine and industrial applications – in essence giving Silverado and Sierra HD customers a lot more truck engine for the money than they realize.
The new Vortec 8100 shares its predecessor Vortec 7400’s valve and bore centers and bore diameter. But its stroke has been increased by 9.4 mm (.37 in.) for a higher displacement and more power. The result is awesome: the Vortec 8100 out-muscles even Ford and Dodge’s V10s!
| Horsepower Torque |
| Manufacturer – Engine |
hp@ rpm |
lb.-ft.@ rpm |
| GM - Vortec 8100 V8 gas |
340 @ 4200 |
455 @ 3200 (617 Nm) |
| Ford – 6.8L V10 gas |
275 @ 4250 |
410 @ 2650 (556 Nm) |
| Dodge – 8.0L V10 gas |
300 @ 4000 |
425 @ 2800 (576 Nm) |
If there is heavy towing or hauling to be done, this is the perfect powerhouse for the job. An impressive 90 percent of its peak torque is available from 1700 rpm to 4300 rpm. And when it comes to acceleration, this engine leaves its competitors in the dust, as the following comparison of comparably loaded, automatic transmission-equipped models shows.
|
0-60 (sec.) |
30-70 (sec.) |
¼-mile (sec.) |
Speed (mph) in ¼-mile |
| At 11,400-lb. GVW load level |
|
|
|
|
| Vortec 8100 with 4.10 axle ratio |
13.4 |
13.8 |
19.7 |
74.0 |
| Ford 6.8L with 4.30 axle ratio |
15.7 |
16.8 |
20.8 |
69.3 |
| Dodge 8.0L with 4.10 axle ratio |
16.3 |
16.7 |
21.1 |
68.1 |
|
|
|
|
|
| At 22,000-lb GCW load level |
|
|
|
|
| Vortec 8100 with 4.10 axle ratio |
25.8 |
26.2 |
25.0 |
59.1 |
| Ford 6.8L with 4.30 axle ratio |
32.3 |
36.0 |
27.0 |
53.9 |
| Dodge 8.0L with 4.10 axle ratio |
32.2 |
34.2 |
27.0 |
54.5 |
Even with the Vortec 8100’s awesome power and performance, its specific fuel economy (per liter of displacement) is four percent better (than the 6.5 liter).
And the Vortec 8100 operates more cleanly; it already complies with 2002 “clean-fuel-fleet” requirements. Its new design also permits running on alternative fuels, including liquid propane gas (LPG) or compressed natural gas (CNG), without requiring any special valves and seats. California versions of the engine are equipped with Air Injection Reaction (AIR) and pup catalytic converters to meet that state’s more stringent emissions requirements.
The Vortec 8100’s 200,000-mile (322,000-km) durability testing includes rigors that no other gasoline engine in its class have been put through; they include running at wide-open throttle for 300 straight hours!
Its low maintenance design requires only normal oil and filter changes during the first 100,000 miles (160,000 kms). Oil changes are based on actual need. The Powertrain Control Module records engine temperature and length of operation at a given temperature, then indicates the need for an oil change with an easy-to-read “Change Engine Oil” LCD message in the Driver Message Center. The driver is also alerted to “Check Engine Oil Level,” when necessary.
Long-life engine coolant is good for five years or 150,000 miles (240,000 kms). A standard coolant level sensor warns the driver of a drop in coolant level. If a catastrophic event causes a total coolant loss, the engine protects itself against damage by running on alternate banks of four cylinders and using cool air to cool itself, enabling the driver to reach a service station.
Advanced Design Features
The Vortec 8100’s rigid cylinder block uses four-bolt main bearings to optimize crankshaft rigidity. The nodular iron crank is internally balanced and counterweighted to minimize internal stresses and bearing loads. The bearings are produced with a new alloy (A260) that increases their life and eliminates the use of environmentally hazardous cadmium. An elastic material called Vamac is used in place of rubber to support the crankshaft’s torsional rigidity: it increases both damping capability and durability. A change in the firing order (to 1-8-7-2-6-5-4-3) reduces main bearing wear and stress on the crank by seven percent.
A coil-near-plug ignition system increases ignition energy by 50 percent, reduces emissions and improves idle quality.
New pistons have a shorter deck height and skirt length; they permit the longer (0.37 inch/9.4 mm) engine stroke, without any significant increase in engine deck height and minimal heat build-up. A Teflon™ coating reduces friction. An especially short (5 mm) top ring land and new full-radius top ring design improve combustion efficiency and reduce exhaust emissions.
New cylinder heads feature replicated intake ports (each precisely equal in diameter and length) for improved fuel-air distribution and a reduction cylinder-to-cylinder variations in torque output, improving operating smoothness and efficiency. Powdered-metal exhaust valve seats and cast-iron guides enhance durability. Five head bolts circle each cylinder to assure reliable lifetime sealing, which is further enhanced by (1.3 mm) thicker, more durable head gaskets.
Hydraulic roller lifters ride on a durable steel camshaft. Stiffer ball-pivot studs support more robust rocker arms. A cast-iron cam-drive cover adds to the valvetrain’s quiet operation.
The aluminum intake manifold’s long, even-length runners yield a broad, flat torque curve plus excellent volumetric efficiency (breathing) at high rpm. The manifold is more precisely made, using a “lost foam” casting technology. It involves making a styrofoam assembly; pouring sand around it and shaking the sand into voids. Molten aluminum is then poured through the sand. It melts that foam, displaces it and cools in the shape of the part. The process permits more intricate internal crankcase ventilation passages that eliminate the need for an external crankcase valve and plumbing. This cuts maintenance costs and eliminates potential leak sources.
Fuel is delivered by a high-pressure (400 kPa) sequential port fuel injection, providing quick starts and smooth operation in cold and hot weather. An Electronic Throttle Control (ETC) meters intake air more precisely. It also reduces weight and enhances reliability/durability by replacing the 7.4 liter’s mechanical hardware with electronic sensors, wires and actuators and integrating functions such as cruise control, brake torque management and traction control into a single controller. The Vortec 8100’s new mass airflow sensor also has an integral temperature sensor to facilitate fine mixture adjustments.
Stainless steel exhaust manifolds (replacing the Vortec 7400’s cast iron) are significantly more heat resistant and durable. Manifold shields keep heat out of the engine bay and muffle the sound of high velocity exhaust flow.
The improved (over the Vortec 7400) cooling system is fully pressurized, it includes a surge tank and a single, aluminum-body double-volute pump. The pump has a durable, cast-iron case, and longer-life silicon-carbide shaft seal. Its redesigned water jackets provide more flow, and it distributes equal amounts to both banks of the cylinder case for greater efficiency. A 100 mm wider radiator provides two more liters of capacity. The transmission cooler has been relocated to boost airflow. A modulating fan clutch provides quieter operation. To prevent any potential leaks, fitting beads and hose ends were designed for tighter, more reliable fit; clamps are specified for optimum pressure and glued in place on hoses to assure proper alignment and secure sealing.
A dual belt accessory drive de-couples the engine’s alternator and accessories from the air conditioning compressor. This reduces loads on the accessory pulleys by up to 50 percent (over the Vortec 7400), improving efficiency and belt life. It also reduces accessory drive noise by nearly 50 percent (7 dBA) at 1000 rpm and further increases interior comfort by permitting the A.C. compressor to be located as far as possible from the passenger compartment. Stiff cast-iron accessory mounting brackets also help reduced noise and vibration. The drive belts are constructed of a new, non-neoprene compound that extends their life to 150,000 miles (240,000 km).
Controlled compression gaskets are used in the oil pan, rocker covers and intake manifold to eliminate leaks. Rocker rails have also been raised to prevent oil from puddling against the rocker cover gaskets.
A three-piece, thermoplastic sight shield adds to the advanced look of this superlative engine.
Vortec 6000: More Standard Power
The Vortec 6000 V8 replaces the previous Vortec 5700 to become the most powerful standard V8 in its class. It delivers 45 more horsepower and 30 lb.-ft. more torque than the Vortec 5700 and also more power and better economy than it did in as used in other 2000 model trucks.
| Horsepower Torque |
| Manufacturer – Engine |
hp@ rpm |
lb.-ft.@ rpm |
| 2001 Vortec 6000 V8 gas |
300 @ 4400 |
360 @ 4000 (488 Nm) |
| Ford – 5.4L V8 gas* |
260 @ 4500 |
345 @ 2300 (468 Nm) |
| Dodge – 5.9L V8 gas* |
250 @ 4000 |
335 @ 3200 (454 Nm) |
|
|
|
| *2000 Model Year Ratings |
|
|
The Vortec 6000 also provides a high, flat torque curve, geared to heavy hauling and trailering, along with a 12,000-pound GVW and 16,000-pound GCWR. It is also designed for 200,00-mile (320,000 km) durability. And it too provides “Change Engine Oil” and other alerts similar to those of the Vortec 8100, along with safeguards, such as the “limp home” feature, which protects the engine and allows customers to reach a service station, even with a total coolant loss. The Vortec 6000 can also be equipped to run on alternative LPG or CNG fuels.
Vortec 6000 Design Improvements
For 2001, the Vortec 6000 features cast-aluminum cylinders, saving a significant 55-pounds (25 kgs) of weight and providing more valve seat durability (than the Vortec 5700). Intake and exhaust ports patterned after those used successfully in the hottest version of the Chevrolet Corvette’s engine yield major gains in volumetric efficiency (better breathing). Valve and lift duration have also been altered to take fully advantage of the free flowing ports, while dual catalytic converters and exhaust pipes minimize back pressure and provide more power.
The Vortec 6000 also has tighter-tolerance main bearings for quieter cold operation (than before), better isolation for the fuel-injection solenoid, a new mass air flow sensor with integral temperature sensor and a more durable coolant temperature sensor (than before).
A larger pilot bearing also provides more durability for the standard (MW3) heavy-duty five-speed manual transmission, available only with this engine only.
Wider Availability of Alternative Fuel Models
Silverado and Sierra offer alternative fuel engine compatibility on any 2500 or 3500 Series pickup or chassis cab, with either the Vortec 6000 or Vortec 8100. The Vortec 6000 requires an (RPO KL5) option to run on these fuels. This provides the engine with especially hardened copper alloy valves and seats to withstand CNG’s and LPG’s dryness or lack of lubricity. With this option, customers can have an upfitter of their choice complete the conversion. The option is not required with the Vortec 8100, which is already gaseous-fuel compatible.
Two other options provide customers with either a fully converted, dedicated LPG fuel system (RPO KL7) or a fully converted, dedicated CNG fuel system (RPO KL8).
These options are available on four ¾-ton models, including the C/K2500 Regular and Extended Cab long box pickups. They are rated at 8,500-pounds (3,856-kgs) GVW. The lower ratings enable fleet and commercial customers to qualify for special credits and monetary incentives provided by the government’s Energy Policy Act (EPACT) and to meet clean fleet requirements in “non-attainment” areas like Denver, where pollution levels are exceptionally high.
With RPO KL7 or KL8, the truck is fully upfitted to LPG or CNG use under GM’s exclusive agreement with IMPCO Technologies of Irvine, California. IMPCO is a worldwide leader in alternative fuel technology. IMPCO’s alternative fuel systems were jointly developed with GM and validated to strict GM OEM requirements. The systems are fuel injected, have the industry’s only truly temperature-compensated fuel gauge reading (taking both the temperature and pressure of CNG into account) and a fast-fill fuel receptacle with the CNG option, called Hyperfill™, that prevents any potential freeze-up.
IMPCO’s alternative fuel systems carry a 36-month/36,000-mile (58,000-km) warranty (five-years/50,000 miles [80,000-kms] on emissions-related components). Chevrolet and GMC dealers handle the warranty work. The systems are certified for use in all 50 states.
New High Capacity Transmissions Further Performance, Economy
The Duramax 6600 and Vortec 8100 mate to new high torque capacity transmissions, with outstanding toughness and driveability for heavy towing and hauling, strong launch and hill-climbing power and unique features, like grade-braking speed control included with the automatic transmission. The new transmissions include an (ML6) standard ZF S6-650 six-speed manual and optional (M74) Allison 1000 five-speed automatic.
Both transmissions feature larger, stronger gears, stronger clutches, more stronger clutch material and other heavier-duty components than those typically found in one-ton truck transmissions. They provide extraordinary 200,000-mile (320,000-kms) durability and customer value. Although validated only for the Silverado and Sierra’s 12,000-pound GVW and 22,000-pound GCWR requirements, both transmissions have the potential of going well beyond those requirements.
ZF S6-650 Geared to Better Performance and Economy
Germany’s renowned Zahnradfabrik Friedrichshaven AG supplies the ZF S6-650. Silverado and Sierra are the first trucks in their segment to offer this transmission with both gasoline and diesel engines. Full synchronization in all gears provides easy shifting. The use of phosphate coated parts (similar to Teflon) throughout the gearbox enhances the slickness of the shifts. The compact design of the synchronizer packages also shortens the shift lever’s travel and provides a tight shift pattern for easier operation. Second and third gears have dual cone synchronizers for extra capacity.
First gear can be used as a “creeper gear” for better low-end performance and towing (than a conventional five-speed manual). Second gear provides enough torque for launching an unloaded or lightly loaded truck. With reverse and first gear in the same shift gate, users can throw the gear lever forward for reverse and straight back for first. This facilitates parking lot maneuvers. It also allows commercial operators to maneuver easily at low speed when engaged in towing or snowplowing. Sixth gear position is forward and away from seat, improving the comfort of the middle passenger, particularly during highway driving.
A high-helix angle gear-tooth design assures quiet operation. The transmission’s extra ratios tighten gear splits, reducing gear-to-gear RPM drop-off and maintaining engine’s operation near peak torque at all times for optimum performance. The extra sixth gear also improves fuel economy (over a five-speed automatic).
The clutch housing is integral to the transmission’s front housing; both the aluminum front and rear housings bolt to a structural intermediate plate, providing sturdy support for the main shaft and countershaft. The use of synthetic lubricant eliminates the need for an external cooler and associated lines, improving reliability and operating costs with its “lubed-for-life” design.
A right-side power take-off (PTO) provision allows our 3500-Series chassis cabs to be equipped with hydraulic pumps, providing up to 25-horsepower capacity. (PTOs are typically used to power auxiliary equipment like dump bodies and hoists and can also be used to power generator sets, compressors or impact tools.)
Allison 1000 Provides PTO Capability, Grade Braking
It is a segment exclusive for Silverado and Sierra. GM’s Allison Division, the leading supplier of automatic transmissions for large application commercial truck and bus markets worldwide, supplies the all-new (M74) Allison 1000 five-speed automatic. Its five forward speeds provide a 30 percent increase in ratio coverage for better launch, grade climbing, towability and high-speed economy (than four-speed automatics). The smaller gear splits also minimize changes in engine RPM and torque for smoother operation.
The Allison 1000 has full electronic control of shift timing. The Transmission Control Module (TCM) automatically selects the gear for each drive range and engages the torque converter lockup. In its normal mode, the torque converter clutch is locked up in fourth and fifth gear. In the Tow-Haul mode, it is engaged in second, third, fourth and fifth gears to avoid heat build-up.
With the fuzzy logic programmed into its controls, the transmission provides a major new benefit called Engine Grade Braking®. If a driver descends a hill, the TCM senses the weight of the load, the vehicle’s speed and the deceleration rate and – based on its calculations – automatically downshifts to a lower gear to help slow the truck. This prevents dangerously overheating the brakes and extends brake life. In its normal mode, it will downshift from fifth to fourth gear when necessary. In the Tow-Haul mode, it will do multiple downshifts – from fifth to fourth, then from fourth to third – using steadily lower gears to help slow the truck on steep declines.
The Tow-Haul mode, a GM exclusive, also provides Shift Stabilization. This reduces “shift busyness” during hill-climbing or heavy hauling/towing by selecting and holding the right gear, based on throttle position, engine speed and other factors. It also makes the shifts more quickly, helping to improve the transmission’s durability under heavy loads.
The Allison 1000 has a massive 310 mm torque converter whose vanes are fully brazed (a metal forming process) to keep them from ever loosening up. Its clutches are designed with automatic compensation for wear. Even as their plates wear, they continually adjust and maintain pressure to provide the same consistently high-level shift quality. Helical-type planetary gearsets provide extra quiet operation.
The Allison 1000 also has a high capacity, 19,850-pound (9,000-kg) parking pawl, which reduces the need to use the hand brake. It also enables one-ton truck customers to install a PTO in an automatic transmission. The PTO allows hydraulic pumps with up to 25 horsepower capacity to be installed on the right side of chassis cabs.
Smooth-Shifting 4L80-E Featured with Vortec 6000
The Vortec 6000 continues to mate two previously available, smooth-shifting transmissions, including a standard New Venture Gear (NVG) heavy-duty five-speed manual and the optional GM 4L80-E four-speed electronically controlled automatic with overdrive.
The 4L80-E’s electronic controls adjust engine torque during shifts for smooth gear changes. A high-extension torque converter contributes to the smooth power transition by sustaining torque output from one gearshift to the next. The torque converter clutch is smoothly engaged and released with a pulse-width-modulated solenoid. The transmission’s Tow-Haul mode prevents shift busyness during heavy hauling/trailer. DEXTRON III lubricant, good for 50,000 miles (80,000 kms), is easy changed with a convenient drain plug in the sump pan.
PTO Enhancements
GM engineers worked closely with PTO installers and major suppliers in selecting PTOs for the widest range of customer needs, creating the right package fits for them and making sure that installation parts were readily available. The PTOs and pumps available for the Allison 1000 and ZF S6-650 can satisfy 90-95 percent of the one ton truck market’s needs.
The chassis cabs can be prepped for PTO installation with a (RPO M1F) packaging option (floor cutout, floor cover, heat shields) and a content option (PTO wiring connector and special Powertrain Control Module features). An aftermarket accessory kit, available from GM Service Parts Operations, also provides an easy-to-hook-up, dash-mounted PTO control switch and a jumper harness (for the transmission wiring harness). This assures quality installations, preventing the kind of problems that arise from aftermarket installers tampering with the dash panel, electrical system and PCM or ECM.
The PTO switch provides “On,” “Set” and “Off:” selections. In the “On,” position, a little flashing LED signals that PTO operation has been requested. The light steadies when the PTO is fully engaged. The engine starts at a low idle. By touching the “Set” position, an operator can increase its speed to the level required for normal PTO operation. Touching “set” again reduces the engine speed back to low idle, thereby allowing the operator to toggle back and forth between the two speeds. Chevrolet and GMC dealers and service outlets with Tech II capability can also adjust the PTO’s operating speed to be higher or lower than the factory’s 1300-rpm engine default setting.
Along with the preset mode, there is also a “mobile/variable mode.” It allows an operator to either drive the truck with the PTO engaged or vary the engine speed at which the PTO operates, when the truck is standing still. The mobile/variable mode operates a lot like cruise control, with the operator using a foot on the accelerator and the PTO switch’s “set” position to establish the engine speed for the PTO’s operation. If the truck is standing still, the speed can also be varied in 50-rpm increments by tapping the “set” position. If the truck has cruise control, it can also be used to control the engine’s speed and, therefore, the PTO’s operating speed by first de-selecting the preset mode and then selecting the mobile/variable mode.”
Electric Shift Transfer Case Added to Improved Lineup
New Venture Gear (NVG)-supplied new manual and electric shift transfer cases that feature a stronger, lighter magnesium construction case (than previous models) and GM’s patented Insta-Trac® for easy shifting into and out of four-wheel-drive at any speed, without leaving the cab. (The vehicle must be stopped to shift into 4LO.) New dual-cone synchronizers improve shift quality at low temperatures (over the previous generation). In addition, the transfer cases have a common large main shaft and chains for increased durability, with small, close chain links providing quieter operation.
The NVG electric shift transfer case available with the automatic transmission is a first for GM heavy-duty pickups and chassis cabs. It provides easy push-button operation and includes a neutral position for flat towing (behind a recreational vehicle). Shift selections include:
- 2HI – Two-wheel-drive for normal roads
- 4HI – Part-time four-wheel-drive only when its required for special circumstances, such as serious off-road operation or in snow or mud.
- 4LO – Four-wheel-drive low, providing a high level of torque for climbing a steep hill or towing a boat up a launch; it can also be used to control the speed of the truck at a very slow pace (thereby eliminating constant braking.)
- Neutral – For towing. To prevent driver confusion, the position is not labeled on the transfer case shifter, but the procedure shifting in and out of neutral is found in the owner’s manual.
Highly sophisticated electrical architecture provides interface with the new Class II bused electrical centers and diagnostic capability designed into Silverado and Sierra HD models. Among them is a “Service 4WD” indicator in the Driver Message Center for monitoring problems.
Stronger Axles, Propshafts
All models offer two axle ratios: 3.73:1 and 4.10:l. Front axles for 4WD applications use a 9.25-inch (235-mm) ring gear. Models equipped with the Vortec 8100 or Duramax 6600 have a new aluminum “Powerdense” case with extra ribbing that provides significantly more strength for the front axle’s external housing structure. They also feature new, massive 11.5-inch (286-mm) rear axles with 13,500-pound (6,124-kg) capacity to handle the higher GVWs, increased horsepower and torque requirements of the engines. Those with the Vortec 6000 feature 10.5-inch (267-mm) rear axles with 10,500-pound (4,763-kg) capacity.
All rear axles benefit from updated processing that yields more consistent control of critical dimensions to assure quieter and more reliable operation. Use of synthetic rear axle lubricant reduces running temperatures by up to 40º F during towing and hauling, thereby improving seal performance, bearing life and overall axle reliability. The lubricant provides a slight increase in fuel economy. A drain plug provides easy rear axle fluid changes.
New propshafts carry more torque and save weight, thanks to key design changes. Weight has been reduced with a larger 3.5-inch (89-mm) outside diameter (up from 3.0 inches/76 mms), which permits a reduction in wall thickness without affecting torque capacity, and by shortening the propshafts. Universal joint life has been doubled by the use of better seals and lubricants. Joints fitted to models equipped with the ZF six-speed manual, which typically encounter the most strain, are 25 percent larger. New 10mm longer halfshafts also improve turning diameters.
Contacts:
Pontiac-GMC Communications
(313) 667-4000
FAX (313) 667-4001
Chevrolet Communications
1-800-CHEVY-MI or (313) 667-9317
FAX: (313) 667-4007
Engine & Transmission Specifications
6.6L V8 Duramax Turbo Diesel
Vortec 8.1L Big Block V8 (L18)
Engine & Transmission Specifications
Allison 1000
ZF S6-650
|
