As compared to the 2010 Chevrolet Silverado’s Duramax diesel, the 2011 model provides a fairly substantial increase in both horsepower and torque (from 365 HP @ 3,200 rpm to 397 HP @ 3,000 rpm; and from 660 ft.-lbs. to a whopping 765 ft.lbs. @ 1,600 rpm). Of course, considering today’s sky-high prices of any maker’s dressed-out turbo diesel trucks (this Chevy Duramax-equipped example lists at $57,254.00), any additional torque/towing capabilities is always appreciated. FYI: The $57K+ price includes the $7,195 Duramax diesel engine option (over the standard Vortec 6.0L gas engine), and the optional Allison 6-speed auto trans, which is another $1,200 over standard equipment.

Driving experience

First of all, the ride is excellent. The steering (although just a bit on the light side) and ride offers enough road-feel to keep the driver connected, while isolating occupants from uneven road surfaces. The ride is firm without being harsh, quiet and darned comfy without feeling mushy.

The brakes are absolutely outstanding. The 4-wheel-disc (rotors appear to be 12-inch) system hauls this truck down now, with a feeling of complete confidence. Aside from long term normal wear, there’s no reason to upgrade the braking system. Chevy got it right with this truck. This is no wishy-washy brake system. This is the braking feel and control I wish <I>every</I> light truck had.

The Duramax 6.6L turbo diesel is a proven powerplant, and like most commercially available turbo diesels, it keeps getting a bit better with every model year. There’s plenty of torque to climb grades and for just about any towing application (tag, gooseneck or fifth wheel). However, the throttle response immediately off-idle felt a bit muddy to me, and not as crisp as I had expected. No bogs, deadspots or stumbles, just a bit slow to initially respond (soft throttle). When you nail the throttle though, she wakes up and quickly says goodbye to the landscape in the rearview mirror. I suspect a bigger air intake and a bit of fuel delivery tweaking will really make a difference, for someone who wants to make a few mods. For the average street driver though, she’s got plenty of go-power.

One thing that really is surprising is how quiet the engine is, at idle and up through the gears. No rattling or clacking at all like an old-school diesel. It’s so quite that it almost sounds like a gas engine. That’s good news, especially for anyone who has never previously owned a diesel truck, and a real surprise for anyone with diesel experience. My 2002 Ford F350 with a Navistar 7.3L turbo diesel makes a real racket compared to this 2011 Duramax (of course, I happen to like the sound of my Nav).

The interior (coupled with the excellent suspension and body mounts) makes this Silverado a real pleasure to drive. I couldn’t expect any truck to ride this smoothly and quietly. The layout of the controls, excellent all-around visibility and the very comfy seat design makes this truck a joy to drive.

One of the (many) luxury features included in this sample truck is the rear vision camera system. A small camera lens is mounted into the tailgate’s handle housing. When the transmission is placed into reverse, the system automatically activates, providing a heads-up display in the windshield-mounted rearview mirror. The camera lens provides a very wide angle field of view, great from a safety standpoint, and handy when backing up to a tag trailer for hookup.

Chassis notes

The driveshaft is heavy-wall aluminum (for weight savings), featuring a hefty 4.75-inch O.D.

The rear suspension features a live axle, multi-leaf springs and offset shocks (the left shock is behind the axle and the right shock is forward of the axle).

The front suspension features torsion bar springs and twin triangulated upper and lower control arms. Camber and caster adjustment is offered at eccentric bushings at the upper arm.

The frame is fully boxed for added rigidity. The front crossmembers are conveniently bolted in, providing access for engine/trans removal.  An additional tubular steel crossmember is located immediately under the front of the driveshaft (which should prevent the front of the shaft from dropping to the ground in the event of a failed front U-joint).

The long longitudinal fuel tank is shrouded by a bolt-on plastic protective cover, and is located on the left side.

The eight cab-body-to-frame bushings are heavy duty cushions (these appear to be a medium-durometer urethane), which would help explain why the ride is so comfy and isolated from road shock (this beast handles rough roads and potholes like a champ… no tooth-rattler here).

Steering is via a recirculating ball gearbox, with linkage attached forward of the front axle.

Engine bay

One of the first things you’ll notice when you pop the hood is that it doesn’t climb up into the sky, slipping off of your fingertips. Anyone who works on trucks knows all too well that sometimes it’s a pain to reach up and grab a truck’s opened hood, especially for guys who are less than tall in stature. The fully opened hood height (ground to hood lip) on this 4WD truck measures a scant 80 inches, as compared to, for example, a 2002 Ford F350 RWD diesel’s 83 inches (keep in mind that this Chevy is a 4WD, so a Ford 4WD hood-open height is even greater than 83 inches). Hey, whenever you can reduce back and shoulder strain in the shop, that’s always a good thing.

The engine bay is cramped, as you’d expect.  The dual battery setup features one battery per side (the right battery is under the hood hinge area and the left battery is up front, immediately behind the headlight area). Access to the brake master cylinder is good… nothing major in the way. The alternator is mounted near center, up high, so no big deal there. The power steering pump is a bit buried on the left front, but the black plastic fluid reservoir is very visible and offers easy access.

[PAGEBREAK]The engine oil filter is easily accessed from underneath (left side rear of the block). The diesel fuel filter is located on the right (passenger) side, under the air intake. The most common method of access is from the right front inner fender (requires inner fender liner removal). To make this easier, you can make a cutout on the plastic fender liner for filter access, and then install a cover panel over the cutout. You can make this panel, or they’re available from various aftermarket sources. This will make fuel filter changes easier, especially in the winter months when the need to change fuel filters increases in cold climates.

The engine’s oil-fill tube is a very heavy duty steel tube, with welded bracing (we can assume that during design development, this must have posed a stress area).

The turbo, as expected, is located behind the intake area. Intake plumbing is fully accessible, but (again, as you’d expect), intercooler plumbing is deeply buried. The engine bay is so busy that you can’t even see the valve covers, so be prepared to remove a bit of real estate to gain access. The turbo wastegate is tucked way back on the right side and down low, so you’ll need long arms to reach. The access issues I’m pointing out aren’t criticisms, but merely the nature of the beast. The front lower shroud/dust cover hides quite a bit, so access to the steering box, pulleys, etc. will be much improved after removing this cover. By the way, the Allison 6-speed transmission features its own external spin-on filter, which is a nice touch.

The Duramax engine features a “common rail” fuel feed system, with a fuel rail dedicated to each bank. The CP3 type fuel pump is located at the front and is gear-driven by the camshaft. Fuel pressure is controlled by the ECM via a pressure regulator. A fuel supply pump moves fuel from the tank to a separate high-pressure pump.

One of the reasons the Duramax is so quiet is due to the use of two types of fuel injection pulses. At engine speeds from idle up to about 2,500 rpm, a “pilot” injection occurs first, spraying a small amount of fuel to start the combustion process, immediately followed by main fuel injection. This basically allows combustion to occur in a sort of stepped process instead of popping the main charge in from the get-go.

Cold weather (we’re talking cold) has always plagued diesel-fueled engines, since the fuel likes to “gel” at freezing temperatures. The Duramax (like other diesels) features feature an intake air heater (IAH) and glow plugs (one per cylinder). The glow plugs heat the combustion chambers, inviting the fuel into a cozy warm environment, free to combust as intended. (diesel exhaust fluid)

Exhaust fluid?

No, that’s not a joke. Anyone who routinely works on diesel trucks is certainly familiar with diesel exhaust fluid (DEF) by now. If you’ve never heard of this before, DEF is one of the key elements involved in the SCR process (Selective Catalytic Reduction, a system enacted starting with all 2010 diesel trucks). It is a nontoxic solution of 67.5% water and 32.5% automotive grade urea (ammonia). Simply put, DEF helps to convert NOx into nitrogen gas and water vapor. DEF is stable, colorless and odorless, and helps diesel engines meet the 2010 tailpipe standard, and supposedly increase fuel economy as well.  Small quantities of DEF are injected into the exhaust stream (plumbed to the converter). As already mentioned, when mixed with NOx, the NOx converts to harmless nitrogen and water vapor. Commonly, DEF refills will coincide with engine oil change intervals. <I>If the DEF is allowed to deplete (not refilled when needed), engine performance may degrade and the engine may not start.</I>

The DEF fill neck on the 2011 Duramax-equipped Silverado is located on the right side of the firewall. The fill neck features a bright blue cap and a very convenient built-in funnel to reduce the chance of spillage.

A note of caution: Pay attention when topping off fluids. Until you’re familiar with this truck, READ the fluid fill caps. Don’t make the mistake of rushing and assuming that the blue-capped fill neck for the DEF is for the tranny, windshield solvent or anything else.  If you accidentally dump trans fluid into the DEF fill, you’re gonna have big problems, and you’ll probably kill the expensive converter.

Engine    Duramax 6.6L Turbo Diesel
Transmission    Allison 6-speed automatic & electronic shift transfer case
GVW rating    10,000 lbs.
Rear axle    3.73:1 ratio & locking rear differential
Front suspension    Independent, torsion bar
Rear suspension    Multi-leaf (Z85 handling/trailering)
Steering    Recirculating ball
Brakes    4-wheel disc ABS

MISC. FEATURES (this list does not include all vehicle features)
Diesel exhaust brake
Tire Pressure Monitoring System (does not apply to spare tire)
20-inch forged aluminum wheels
LT265/60R20 tires
Adjustable pedals
Stabilitrak stability control with trailer sway control and hill start assist
125-amp alternator
Cruise control
Rear vision camera system (in-mirror video)
Camper style heated/power adjustable door mirrors
Battery run-down protection
Oil life monitor system

PERFORMANCE SPECS
Horsepower    397 @ 3,000 rpm
Torque    765 ft.-lbs. @ 1,600 rpm
Max conventional tag towing    17,000 lbs.
Max 5th wheel towing    21,700 lbs.
Max payload    4,192 lbs.
Max front gross axle weight rating    6,000 lbs.

DURAMAX ENGINE SENSORS

MAF (Mass Air Flow)

IAT (Intake Air Temperature)

CKP (Crankshaft Position sensor). This is located on the front engine cover. 57X signal.

CMP (Camshaft position sensor). Also at the front engine cover. 3X signal.

ECT (Engine Coolant Temperature sensor)

BP (Boost Pressure sensor). Placed inside the intake manifold. Serves as a MAP sensor.

FRP (Fuel Rail Pressure sensor)

FT (Fuel Temperature sensor). This is mounted in the return line, providing info to the ECM.

Low oil level sensor/switch (located in the left wall of the oil pan sump)

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