BUMPER TO BUMPER COVERAGE
Everything you need to know about the 2017 Silverado HDS
With an all-new Duramax boasting a best-in-class 445 hp, improved braking and towing technology, and an Allison 1000 that's as steadfast as it's ever been, there is a lot to like about the '17 Chevrolet Silverado HDS. And even though GM has chosen to sit out the GCWR war currently raging between Ford and Ram for the time being, it doesn't mean the General has been sitting idle. Instead, the cab that was introduced in '15 has been further refined, fuelrelated failures have likely been curbed thanks to an entirely new high-pressure common-rail injection system, and state-of-the-art trailering technology has been added to make the towing experience as safe and as comfortable as possible.
Fortunately, after Chevrolet cordially invited us to get behind the wheel of several ’17 model HD trucks, we were able to see all of the aforementioned improvements firsthand. To experience the L5P Duramax engine’s class-leading horsepower and stout 910 lb-ft of torque, we piloted an unladen 2500 HD model up and down the highway. After that, we hooked it to 13,000 pounds’ worth of trailer and construction equipment to put the truck through its paces in a real-world work environment. Then to find out how stable Chevrolet’s dually model feels at its maximum rated towing capacity, we joined a 3500 HD to a 33-foot gooseneck trailer loaded with a 7.5-ton backhoe.
In our time behind the wheel of Chevrolet’s newest trucks, we found that the ’17 HDS are unequivocally the quickest diesel trucks on the road today. Loaded or unloaded, the latest Bow Tie not only offers some of the strongest acceleration we’ve seen, but the combination of its fine-tuned exhaust brake, quick-reacting integrated trailer brake controller, and engine braking (courtesy of the Allison 1000 transmission’s timely downshifts) make it one of
the safest heavy-duty pickups on the market today. Did we mention that Crew Cab 4x4 model 2500 HDS can run high 14-second quarter-miles in bone-stock trim? With a boosted four-wheeldrive launch, we’ve seen several ’17s run 14.80s and 14.90s in the 92-93mph range, which signifies that nearly 400 of the engine’s 445 hp is making it to the wheels.
Despite being built on the same overall platform that debuted in 2011, Chevrolet has added key improvements to its proven design. New parts and technologies employed on the ’17 trucks start with a cosmetically appealing yet fully functional hood scoop to control intake air temps for maintaining peak power on long grades. A larger, more efficient turbocharger combines with higher-flowing, cast-aluminum cylinder heads for a 20-percent improvement in airflow. A closed-loop glow plug circuit is employed for quicker cold starts. The inclusion of a factory-installed low-pressure fuel supply system adds durability and longevity to the high-pressure common-rail fuel system. And finally, through various enhancements performed on the selective catalytic reduction system, considerably less diesel exhaust fluid is consumed to meet emissions requirements.
In the bumper-to-bumper coverage of the ’17 Silverado HD that follows, you’ll get the full rundown on the latest powertrain specs, a comprehensive list of Chevy’s newest features, and our take on what we like and don’t like about the General’s latest heavy-duty. After getting behind the wheel of these trucks and spending some time with Chevrolet Silverado HD Chief Engineer, Erik Stanczak, it’s clear that the latest Silverado 2500 and 3500 are the cleanest-burning, most powerful, and safest workhorses GM has ever produced. UDBG
The 2017 Chevrolet 2500 HD and 3500 HD trucks are greatlooking trucks that offer incredible performance to back up their good looks.
Even though the new L5P code Duramax displaces 6.6L, it shares little else with the engines that preceded it. The block, crank, rods, pistons, cam, and heads are all new. To hold up under the added cylinder pressure required to produce the L5P’S 910 lb-ft of torque, GM heat-treats the deep-skirt, cast-iron block—which accounts for a 20-percent improvement in overall strength.
The connecting rods were also the beneficiaries of a 20-percent improvement in strength to hold up to the L5P’S immense torque. The powdered metal, fractured-cap rods feature wider rod bearings and offset bearing caps to increase internal clearance for the crankshaft. At the small end of the rods, larger diameter wrist pins are employed to anchor a first for the diesel pickup segment: re-melted pistons. To add strength to the cast-aluminum units, the rim of the piston bowl is reheated after casting and machining, enhancing the metallurgy’s thermal fatigue properties. Note the cutaway view of the cylinder head that shows a much larger intake runner volume (L5P shown on the left compared to previous Duramax on the right).
With exhaust gas temperature such a major concern (especially when towing heavy at maximum engine load), GM tells us that the primary reason behind the hood scoop is to sustain full power on long grades. In years past, the truck’s ECM could de-fuel (i.e., de-rate) the engine in an effort to keep EGT in check. With ample, cooler ambient air coming in via the hood scoop, it’s believed that the new L5P Duramax won’t ever have this problem.
Breaking away from Bosch for the first time, the L5P Duramax makes use of a high-pressure common-rail fuel system from Denso. At the heart of the system rests a Denso HP4 injection pump (shown). The HP4 incorporates a 3-cylinder design vs. the 2-cylinder Bosch CP4.2 found on the ’11-16 LML Duramax, and is capable of producing up to 29,000 psi. Another first for the Duramax, the ’17 trucks come equipped with an electronic in-tank lift pump from the factory. It sends approximately 58 psi (4 bar) worth of diesel the HP4’S way.
To meet the air demands of the L5P Duramax, more than 40 percent of its airflow comes from this location—a fully-functional hood scoop. An integrated expansion chamber, complete with a drain and access plug for debris removal, allows air to pass through it while capturing liquid and solid debris.
The commercial-grade Allison transmission option has always been a great selling point, but now it’s as polished as it’s ever been. Like the rest of the truck, slight improvements had to be made to the six-speed automatic to handle the newfound power of the L5P engine. Among the upgrades were a larger output shaft yoke, a torque converter with an upgraded damper, and an improved TCC valve to aid lockup. As expected, the Allison/duramax combo works in perfect harmony, no matter the condition, and it remains a chore to try to get transmission temp to even break a sweat.
For the driveline to cope with the added grunt, thicker-walled driveshafts (on both 2500 and 3500 models) and the use of 1485 series Spicer U-joints (vs. the 1410s used on ’16 HDS) are now employed. The proven rear AAM 1150 axle remains unchanged, and is still graced with the same auto-locking, limited-slip differential. The only available ring and pinion option is the 3.73:1 axle ratio.
With GM severing ties with longtime supplier Garrett in favor of a uniquely designed unit from Borgwarner, a fresh turbocharger also made its way onto the L5P Duramax. The new variable geometry turbo utilizes a dedicated oil circuit separate from the engine oil, and one of two diesel oxidation catalysts (DOC) is bolted to the back of the turbine housing. Maximum boost (in stock form) checks in at a healthy 28 psi.
Advanced, solenoid-style Denso G4S Gen III injectors, which offer comparable performance to the previous Bosch piezoelectric units, take care of in-cylinder fuel distribution. The Gen III units incorporate 7-hole, mini-sac nozzles that feature a 180-degree spray pattern for optimum atomization, a cleaner burn, and reduced particulate matter.