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GMC Sierra Heavy Duty trucks apply big muscle for tough work
Bob Plunkett
Date Posted: 5/10/2005
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SPRINGFIELD, Mo. -- On a hilly course through the Ozark Mountains of southern Missouri, a big trailer -- packed with dead weight equivalent to a load of two big horses -- trailed behind a four-door rendition of the hefty workhorse pickup truck that bore a bold red-letter nameplate from the GMC Truck Division of General Motors.
This particular truck, a prototype for the new Sierra HD (Heavy Duty) line in one-ton 3500HD series with four-wheel-drive, had an extended cab with front bucket seats and a small rear bench, as well as a long-box bed in back stretching for eight feet.
Beneath the expansive front hood, our truck contained a new Duramax 6600 6.6-liter V8 direct-injection turbo-diesel engine that produces as much as 300 hp plus enormous torque -- up to 520 lb-ft at 1800 rpm.
The plant connected to a remarkable Allison 1000 five-speed electronic automatic transmission. A sophisticated transmission control module in the transmission acts to choose gears and engage the torque converter lockup.
For towing a trailer like the one trailing behind our rig, this intelligent transmission in Tow-Haul mode stabilizes shifting by automatically selecting an ideal gear after sampling various factors, such as engine speed and throttle position.
On long downhill grades in the Ozarks, the transmission control module actually downshifted repeatedly without driver prompting -- from fifth gear down to fourth, then down further to third when needed. It dropped to lower gears to retard the weighty truck-trailer rig on the downhill slope and save brakes from dangerously overheating.
In effect, the transmission package erased all traces of effort related to the chore of driving this trailer-toting truck. All we as driver did was grip the steering wheel and keep the prow pointed in the right lane.
Reducing driver's workload becomes an apparent theme with new designs for Sierra HD trucks, which represent the upward expansion of GMC's full-size line of Sierra pickups.
Cast on a new modular platform that varies in length for different cabin and box sizes, these big work trucks display fresh exterior styling with ornate grillework and muscular shoulders over color-keyed wheelwell flares.
They also offer a new series of powertrains that muscle up to the head of the hefty truck class in terms of horsepower, engine torque and efficiency for towing and toting heavy loads.
Despite their grand scale and class-leading power packages, Sierra HD trucks also tote user-friendly drive and handling hardware and they provide unusually comfortable passenger compartments in cabs rigged with two or four doors, seats for as many as six riders and trappings to rival a luxury car.
With three trim choices and more than 30 different configurations for cab and bed and powertrain and traction, the Sierra HD series consists of a complex array of models that can be bare and simple at one extreme or refined and luxurious for the other.
The series includes 2500HD three-quarter-ton and one-ton 3500HD trucks with cab dimensions of regular and extended lengths plus a four-door Crew Cab, two traction systems in rear-wheel-drive and four-wheel-drive formats, and choices for two gasoline-driven V8 engines plus the Duramax turbo-diesel.
Sierra with the regular cab has a bench seat for three and two front-hinged doors with a back box of long (97.6 inches) length, or the Chassis Cab design in back with no box to support specialized equipment like a wrecker's hoist.
The extended cab edition gets rear cabin doors hinged on back edges. They close by tucking behind the front doors and open in the absence of center pillars to provide a broad and unencumbered space for easy entry to both the front bench seat or a rear three-person jump seat. Either a short (78.7 inches) box or the long box works with the extended cab, as well as the Chassis Cab with back box deleted.
A Crew Cab for Sierra has an even longer cabin to craft a larger rear seat area that accommodates a full-size bench seat for three. Conventional front-hinged rear doors join similar front doors in the manner of a four-door sedan.
Designs for this new series originate with a structure developed for the half-ton Sierra light-duty trucks. Compared to the previous Sierra HD trucks, new ones have expanded-width front and rear wheel tracks to forge a wider and more stable platform.
A new suspension system applies with independent front long-and-short arm and torsion bar springs. Semi-elliptical multi-leaf springs in back deploy in two stages for the 2500HD trucks and in three stages for 3500HD one-ton models.
Steering, with power assistance for the integral recirculating ball device, was tuned to produce more driver control with improved on-center feel and crisp swing action.
For braking such a big machine, a big disc mounts at each wheel with hydro-boost power control and the link to a computerized anti-lock system.
Standard safety elements range from dual frontal air bags to seat-mounted three-point safety belts, child security locks for rear doors and daytime running lamps, with some trim levels also listing as standard equipment the OnStar communication and assistance system for in-vehicle security and information services.
Class-leading muscle defines the Sierra HD trucks.
The Vortec 6000 6.0-liter V8 serves as Sierra's base engine and develops more power and torque than any other standard engine in the heavy duty class. Output rises to 300 hp at 4400 rpm, with torque skewed to 360 lb-ft at 4000 rpm.
A five-speed manual transmission or the GM Hydramatic 4L80-E four-speed automatic goes with the Vortec 6000.
New Vortec 8100 8.1-liter big-block V8 scores as an optional plant, generating a stunning 340 hp at 4200 rpm and 455 lb-ft of torque at 3200 rpm. It combines with either a ZF six-speed manual or the intelligent Allison 100 five-speed automatic.
That Duramax 6600 6.6-liter V8 direct-injection turbo-diesel puts out the king-of-the-road power and torque ratings, and it also links with either the ZF manual or Allison automatic.
With these powertrains, the Sierra HD trucks develop the highest gross vehicle weight ratings (gvwr) in class, extending to 9200 pounds for the three-quarter-ton 2500HD and up to 11400 pounds for the one-ton 3500HD series or as much as 12000 pounds with a Chassis Cab in four-wheel-drive.
Trailer tow ratings also peg the ceiling for this class of trucks. For a standard trailer, the rates run to 12000 pounds for either the Vortec 8100 gas V8 or Duramax 6600 diesel, but the fifth-wheel or gooseneck trailer ratings bump even higher -- to a maximum of 15300 pounds for certain configurations.
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| Vehicle Specifications: |
| 2001 GMC SIERRA HD Specs |
| Description: |
Full-size super-strength truck |
| Model Options: |
Full-size super-strength truck |
| Trim Options: |
SL / SLE / SLT |
| Configurations: |
2-door Reg. Cab Long Box, 2-door Reg. Cab Chassis, 4-door Ext. Cab Short Box, 4-door Ext. Cab Long Box, 4-door Ext. Cab Chassis, 4-door Crew Cab Short Box, 4-door Crew Cab Long Box, 4-door Crew Cab Chassis, |
| Wheelbase: |
133.0 inches, 137.0 inches, 143.5 inches, 153.0 inches, 157.5 inches, 161.5 inches, 167.0 inches, 185.5 inches |
| Overall Length: |
222.1 inches, 225.0 inches, 227.7 inches, 237.3 inches, 246.6 inches, 246.7 inches, 249.5 inches, 256.2 inches, 273.5 inches |
| Engine Size: |
OHV 6.0-L V8, OHV 8.1-L V8, OHV 6.6-L V8 TD |
| Transmission: |
6.0-L: (Manual/5, Auto/4) 8.1-L: (Manual/6, Auto/5) 6.6-L: (Manual/6, Auto/5) |
| Drive: |
Rear 2WD, 4WD |
| Braking: |
Power 4-disc/ABS |
| Airbags: |
2 (front) |
| Gross Weight: |
2500HD: 9200 pounds, 3500HD: 11400 pounds, Chassis: 12000 pounds |
| Towing Capacity: |
15800 pounds |
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