Tow Test: 2011 CHEVY SILVERADO
An inside look a the refreshed GM heavy duty diesels; more emphasis placed on tow and go
by Larry D. Walton
“Safety First” is not just a slogan for many contractors, it’s a way of life.
If you’re the guy who insists on hard hats, safety glasses and ear protection, you are likely to be concerned about safe driving for your family and your employees as well.
Safety while towing big trailers is the biggest benefit I see to the combination of changes GM made to their heavy-duty pickup lineup.
Chevy Silverado and GMC Sierra 2500HD/3500HD just got more power, stronger frames, bigger brakes, a diesel exhaust brake and trailer sway control —enough to make safety conscious pickup owners sit up and take notice.
I drove the new GMs while towing a variety of trailers in Pennsylvania, Maryland and West Virginia. The Duramax-Allison combo continued to prove itself pulling long, steep grades.
It was coming back down those hills, however, where the Silverado and Sierra impressed.
The coordination of the turbo charger, Duramax diesel engine and Allison transmission via computer provided one of the best features of the new 2011 HDs: a highly integrated exhaust brake system.
Combined with the grade brake and cruise grade braking features that have been in place for several years, the new exhaust brake greatly improves safety for steep country hauling.
The new, driver-selectable feature uses the compression power of the 6.6L Duramax engine to improve vehicle control and reduce brake pad wear.
When the exhaust brake is engaged in cruise mode, exhaust cruise grade braking will help the cruise control system maintain the desired vehicle speed when travelling downhill, keeping the driver from having to apply the brakes and exit cruise control to maintain speed.
When the exhaust brake is engaged in non-cruise mode, the transmission and the exhaust brake deliver the correct amount of braking to assist in vehicle control, regardless of vehicle load.
The engagement of the system is smooth and quiet, but I knew it was working. In fact, I hardly had to touch the brake pedal in many downhill towing situations over the two days of testing in the Mason-Dixon line hill country. Since the exhaust brake system was working so well, I knew I had plenty of vehicle brakes when needed.
The revamped brakes, those on GM’s new HDs deliver smoother, more immediate and confident-feeling performance. Four-wheel, four-channel ABS comes standard on all single-rear-wheel models and a three-channel system is standard on dual-rear-wheel models.
The larger diameter (14-inch) and width of the front and rear rotors support their increased capacity, weight ratings and trailer tow ratings, and benefit from stiffer, stronger calipers.
The GM guys also revised the calibration of the hydroboost brake booster, which means less force is needed on the pedal giving it a more confident feel.
Larger wheel hub and bearing assemblies complement the new brake system and the rear rotors attach to the wheel hubs for easier servicing.
In addition to improved braking, GM added a trailer sway control system that senses sway and intervenes with braking and/or reduced engine power to bring the trailer under control and keep it on its intended path.
The system uses electric trailer brakes when a trailer is plugged into the standard wiring harness of the truck and its performance requires no input from the driver.
Testing a trailer sway-control system is not something I wanted to do on a public highway, so we’ll take GM’s word on how well it functions.
However, I could test the new hill start-assist system, which automatically engages when sensors detect a grade of about 5 percent or greater.
It holds the brakes for about 1.5 seconds or until the accelerator is pressed, giving the driver time to switch from the brake to the gas pedal without rolling.
It works and that’s good news when someone in a compact car pulls up close enough to disappear behind the trailer.
TOUGHER THAN BEFORE
The enhanced Allison 1000 transmission for 2011 is strengthened to handle the higher torque capability of the new 6.6L Duramax engine.
Reduced “spin loss” delivers greater efficiency – meaning the transmission channels more of the engine’s power to the axles, allowing it to do more with less fuel.
GM’s tranny guys also increased converter lock-up.
The Allison’s torque converter is “locked” at the same speed as the engine more often. Reduced slippage means better use of engine power, improved fuel economy and increased tranny life.
Some of the biggest changes to the 2011 GM HDs cannot be seen without crawling under the truck.
GM showed us a rolling chassis that was split down the middle—one half old chassis and the other new so we could see the difference.
Not only were the new, fully-boxed frame rails obvious, almost every cross component on the new chassis looked stronger as well. I can attest that the entire package feels stable while towing.
The stable platform includes a completely redesigned independent front suspension system that offers up to a 25-percent greater front axle weight rating –GM’s signature short-long arm/torsion bar front suspension design is retained, but now features new, forged steel upper control arms that are stronger and lighter than their predecessors.
Five different torsion bar rates support five different front-gross-axle-weight ratings (a single torsion bar was previously used for all models).
Changes to the rear suspension feature a larger, asymmetrical leaf spring design that also contributes to improved ride and handling characteristics.
The suspension felt stable and smooth, but as I said, I was hauling and towing some big loads and it’s typical for any heavy duty to ride smoother while loaded.
The GM trucks have improved as mobile offices with the addition of an available WiFi system that essentially makes the truck a moving WiFi hotspot.
Attention was given to USB connectivity, Bluetooth connectivity, multiple storage compartments and multiple 12v charge points. However, there were no 120v inverter outlets. We are also still looking for a good laptop holder that you can swing into place while parked.
Heavy-duty pickup owners who use their trucks to tow and haul big loads will benefit from increased power and stronger frames.
But the biggest improvement is in how these changes combine with the exhaust brake and anti-sway technology to make these pickups safer when handling heavy loads.
If you are a Chevy or GMC owner who pulls big trailers, you will want to consider upgrading to the new 2011 GM Heavy Duty Pickup.
While GM says a weight-distributing hitch is not required on the new HD pickups (see “Bad Bow-Ties,” Spring 2010), they did have W-D hitches in place for the conventional (non-gooseneck and non-fifth-wheel) trailers we were towing in Maryland.