New Colorado ZR2 Takes Off-Roading to New Heights

The new 2017 Colorado ZR2 (Fig. 1) is designed to excel off-road, whether that’s tackling out-of-the-way two-tracks, technical rock crawling, or desert running. At its introduction, the ZR2 boasts more off-road technology than any other mid-size pickup.

 

Fig. 1

 

Compared to the standard Colorado, the ZR2 has a 3.5-inch (89 mm) wider track and a suspension lifted an additional two inches (50 mm). Its rugged off-road capability is enhanced with cast-iron control arms; functional steel-tube rocker protectors; aluminum skid shields protecting the radiator, engine oil pan and transfer case; front and rear electronic locking differentials; and the first application of Multimatic Dynamic Suspensions Spool Valve (DSSV) damper technology.

 

ZR2-specific components include:

  • Suspension system
  • Electronic locking differentials
  • Rear axle
  • Rear drive shaft
  • Rear leaf springs
  • Skid shields
  • Control arms
  • Front halfshafts
  • Steering gear and knuckles
  • Coil springs
  • Stabilizer bar
  • 17-inch wheels and all-terrain 31-inch tires (overall diameter)
  • Side rocker protection
  • An optional cargo bed-mounted, full-size spare tire carrier.

 

Powertrains

 

The ZR2 is available with two powertrain choices:

  • A 3.6L V6 gasoline engine (RPO LGZ) and 8L45 8-speed automatic transmission (RPO M5T)
  • A 2.8L L4 turbocharged Duramax diesel engine (RPO LWN) (Fig. 2) and 6L50 6-speed automatic transmission (RPO MYB)

 

Fig. 2

 

The DOHC gasoline 3.6L V6 engine generates 308 horsepower and 275 lb.-ft. of torque. It features variable valve timing (VVT), Active Fuel Management (AFM) and direct injection. The engine contains a dual-pressure control and variable-displacement vane pump that enhances efficiency by optimizing oil pressure as a function of engine speed. The oil pump is located beneath the cylinder block inside the oil pan. Use ACDelco dexos1 5W-30 viscosity grade engine oil.

 

The DOHC, direct-injected, turbocharged 2.8L Duramax diesel engine produces 186 horsepower and 369 lb.-ft. of torque. Engine efficiency and performance is improved by the water-cooled variable geometry turbocharger (VGT) that uses an oiling circuit with a dedicated feed to provide increased pressure at the turbocharger and faster oil delivery. The engine uses an integrated engine oil filter and integrated engine oil cooler. The oil filter is a cartridge-style paper filter designed for easy accessibility in the vehicle. Use ACDelco dexos2 5W-30 viscosity grade engine oil.

 

Transfer Case

 

The 2-speed automatic, active transfer case (ATC) offers five modes: Auto 4WD, 4HI, 4LO, 2HI and Neutral. The automatic transfer case shift control knob (Fig. 3) is located on the instrument panel. The indicator mark on the switch must line up with the indicator light before a shift can be commanded. To command a shift, rotate the shift control knob to the desired position. The light will blink when the shift is in progress. When the shift is completed, the new position will be illuminated. If the transfer case cannot complete a shift command, it will go back to the last chosen setting.

 

Fig. 3

 

The transfer case knob also features an Off-Road Driving Mode that maximizes performance on terrain with limited traction.

 

Off-Road Mode:

  • Interacts with the axle locking system, allowing the vehicle to travel at higher speeds with a locked rear axle.
  • Modifies the sensitivity of the accelerator pedal for fine linear control of torque on uneven terrain.
  • Modifies the transmission shift map to hold gears for a longer period of time, providing limited slip while driving over obstacles.
  • Optimizes the chassis control calibrations.
  • Optimizes the performance of the ABS, traction control, and StabiliTrak systems on slippery surfaces.

 

ELocker Differentials

 

The ZR2 is equipped with an Eaton ELocker differential on the front and rear axles. The ELocker is an electronically-controlled, selectable On-Off locking differential that provides 100 percent axle lock on demand. The differential can operate in an open position, where it channels torque to the low traction wheel, or a fully locked position.

 

The lockers are activated using the switches (Fig. 4) on the instrument panel. LED lights on the switches indicate when the switches are on and the status will appear on the off-roading screen on the Driver Information Center (DIC).

 


Fig. 4

 

To lock the rear axle, press the rear axle locking switch with the vehicle moving less than 25 mph (40 km/h). The rear axle is locked when the light on the switch remains illuminated.

 

The locking rear axle will disengage when vehicle speed exceeds 25 mph (40 km/h). The Off-Road Mode allows the axle lock to remain engaged at higher vehicle speeds.

 

To give the vehicle additional traction when driving through mud or snow and over steep hills or uneven terrain, the front axle also can be locked.

 

TIP: Before the front axle can be locked, the rear axle must be locked and the transfer case must in 4WD Low.

 

Press the front axle locking switch with the vehicle stopped or moving less than 25 mph (40 km/h). The front axle is locked when the light on the switch remains illuminated. Locking the front axle will disable Hill Descent Control and the anti-lock brakes (ABS), illuminating the ABS light.

 

The locking front axle will disengage when vehicle speed exceeds 25 mph (40 km/h) or the transfer case is shifted out of 4WD Low.

 

Multimatic DSSV Suspension

 

The ZR2’s standard Multimatic DSSV™ (Dynamic Suspensions Spool Valve) Position-Sensitive Damping (PSD) system (Fig. 5) is tuned to handle a wide range of terrain, such as rugged trails, deep sand and mud. In these types of extreme wheel travel conditions that are often encountered while driving off-road, the PSD system uniquely optimizes damping response with the precision of spool valves, yet it also provides refined on-road driving dynamics.

 

Fig. 5

 

There are three spool valves in the ZR2-specific dampers. Each valve has laser-cut ports precisely controlling oil flow in response to the damper’s internal pressure for ultimate performance.

 

PSD system components (Fig. 6) include:

1. Off-road bump range compression spool valve
2. Off-road rebound range valve
3. Normal road operating range compression and rebound spool valves
4. Nitrogen-charged reservoir
5. Normal road operating range ports

 

Fig. 6

 

For additional information on the new 2017 Colorado ZR2, refer to Bulletin #17-NA-061.

 

– Thanks to Charles Hensley and Sherman Dixon

 

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