The Duramax gets class-leading power and torque for 2011, and the Allison 1000 Series tran
The news accompanying all the technical renovations was the increase in work capacity. Using the popular Crew Cab diesel (SRW) as an example, the maximum 2500HD GVW has jumped from 9,200 to 10,000 pounds (2,523- to 3,125-pound payload), with a GCVW bumped from 23,500 to 24,500 pounds. The 3500HDs go from a 9,900-pound GVW to 11,600 pounds, and the payload jumps from 2,933 to 4,165 pounds. The GCVW remains the same as the 2500HDs.
Reading the technical nitty-gritty is one thing, but experiencing how they translate to a driving experience is another thing altogether. You'll first notice the uprated diesel's truly "yeehah" performance, empty or loaded. It's stunning how fast these trucks could take a 9,300-pound load to 60 mph going uphill against a 6-percent grade. On 5- to 7-percent grades with that load, the truck cruised at the speed limit in top gear and with the converter locked. With the multifunction info center button set to read "Trans Temp," we didn't see much more than about 165 degrees with the Allison and just under 200 with the 6L90 on the gas trucks, showing GM has tight control of transmission oil temps under load. The truck's ride and handling, both loaded and unloaded, is definitely in the outstanding category for it class.
Even more impressive was how the exhaust brake and Grade Braking features worked, even in cruise control. The exhaust brake system is activated by a button on the dash and uses the variable-geometry vanes on the turbo impeller to restrict the air flowing out of the engine. Full engagement is limited to when the throttle pedal is at zero and the torque converter is locked. It will block the exhaust right to the limit of the turbine's inlet pressure maximum.
There were plenty of opportunities to tow test the new HDs, including using a pair of 9,30
The Grade Braking feature works with or without the exhaust brake activated. The TCM (Transmission Control Module) can sense a grade and uses the transmission to slow the truck. Apply the brakes on a grade, and the Grade Braking software takes over and automatically drops down a gear or two while keeping the converter locked.
Grade braking and the exhaust brake get even more aggressive in Tow/Haul mode. Both systems will integrate with the cruise control to automatically maintain the selected speed-even with a heavy load. On top of all this, there is a mode button on the shifter to manually shift the trans. All in all, this setup is a control freak's dream, and the systems work together almost seamlessly.
As impressed as we were with the stellar performance of the new HD GM trucks, we have a gripe. Overall, GM could improve the control layouts and ergonomics. Especially at the upper end of the options food chain, these trucks have a dazzling array of driver-controlled gizmos that can lead to confusion and distracted driving. With this many driver input options, the type and layout of these controls becomes vital. GM knows well how to do this, and when these trucks are refreshed cosmetically, it's seems likely they will improve the situation. We'd also like to see a power feature for extending the mirrors for towing.
Minor gripes aside, our impressions of the trucks after two day test could be described with two words-consummate performance. The truck leaves you with the impression it's never really working up much of a sweat. The NVH is under tight control and the ride is at the top of the class. GM didn't introduce a lot of show for the 2011 HDs, but they sure delivered a bunch of go.
Viscerally potent 400hp Duramax, exhaust brake and Grade Braking systems, substantially higher payload and tow ratings.
Control system layouts need simplification and integration.
Consummate, pack-leading truck performance.
Updated diesel emissions regs mandated improvements in NOx (Nitrogen Oxide) emissions. Lik
- Vehicle/Model: 2011 GMC Sierra HD 2500HD Crew Cab SLT
- Base Price: $44,560
- Engine(s): 6.0L Vortec OHV V8 (std), 6.6L Duramax V-8 diesel (opt)
- Transmission(s): 6-spd 6L90 automatic (std), 6-spd Allison 1000 (opt w/diesel)
- Transfer case: Part-time 2-spd, MP1626 (electric-shift) or MP1226 (manual-shift)
- Low range ratio: 2.68:1
- Frame type: Ladder, fully boxed
- Suspension, f/r: independent SLA, torsion bars/asymmetrical, variable-rate leaf springs
- Ring and pinion: 3.73:1 (std, 4.10 optional w/6.0L)
- Max crawl ratio: 30.98:1 (diesel), 40.28:1 (gas, 3.73)
- Steering: Power, recirculating ball
- Brakes: 13.97x1.57 discs
- Wheels: 17x7.5, steel or alloy, 20x8.5 alloy opt. (others optional)
- Tires: LT265/70R17 or LT265/60R20 all-terrain (others optional)
- Wheelbase (in): 153.7 (shortbox), 167.7 (longbox)
- Length (in): 240.1 (shortbox), 259 (longbox)
- Height (in): 78.3
- GVWR (lb): 10,000
- Base curb weight (lb): 7,208 (shortbox), 7,387 (longbox)
- Max towing capacity (lb): 13,000 (ball hitch), 15,600 (fifth-wheel)
- Fuel Capacity (gal): 36