Ev­ery­thing you need to know about the 2017 Sil­ver­ado HDS

Ultimate Diesel Builder's Guide - - Contents - Text: Mike Mc­gloth­lin Pho­tog­ra­phy: Mike Mc­gloth­lin & cour­tesy of Chevro­let

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.

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