Brian’s Beat: New Truck, New Era

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Big changes can be found on the new Sierra's braking system. (Photo: Brian Early)

In the first of an occasional series, I provide a look at new vehicles from a service repair technician’s point of view.

Sometimes it’s a good idea to know what kind of vehicles we will find in our independent shop service bays over the next few years. As a technician myself, I was given the opportunity to share one of GMC’s newly redesigned Sierra AT4 pickups and thought it would be interesting to share my observations from a technician’s point of view.

For 2019, General Motors redesigned its half-ton GMC Sierra and Chevy Silverado counterpart. For 2020 it is introducing updated versions of its HD heavy duty trucks. Not too long ago, I was given a chance to sample one of the new GMC half-tons and here is what I found.

Still a traditional, body-on-frame pickup, the current GMC Sierra is larger by several centimetres in all exterior dimensions than the 2018 models, though the popular crew cab’s short box remains the same length at 5’8”.

Five gasoline engines are available, all featuring some form of cylinder deactivation; four 5th generation small block V-engines (a 285 hp 4.3L V6, two 355 hp 5.3L V8s, and a 420 hp 6.2L V8), which are joined by an allnew 310 hp 2.7L turbo inline 4. For 2020, a 277 hp 3.0L turbo Diesel inline 6 will become optional as well. Transmission choices include 6, 8, and 10-speed automatics.

Engine bay overview
Our tester featured the top 6.2L V8 with the AT4 model’s available Off-Road Performance Package, which includes the oiled-cotton air filter visible here and a throatier cat-back exhaust system good for 15 additional horses (now 435). The 5.3L’s underhood layout should otherwise be virtually identical.

The air intake, fuse box, and coolant tank have all been repositioned, but the alternator fortunately remains readily accessible on top. As before, a separate belt runs the A/C compressor, however both belts now appear to be the “stretchy” tensioner-less type.

Engine oil requirements for the V8s continue to be 0W20 meeting Dexos1 spec (gas 4 and 6 cylinders require 5W30). With a filter, V8’s hold 7.6 litres.

Annoyingly, GM has also followed the industry trend by no longer providing a transmission dipstick.

New body structural members effectively narrow the engine compartment, but the inner fenders do seem like they’ll provide service access once removed. Access to the rear of the headlights has improved, though ironically all but lower trim models use non-serviceable LED lamps for virtually all of their illumination.

Front suspension
It may still use a double-wishbone style front suspension with coilover struts, but the components are entirely new. The lower arms switch from cast to stamped tubular, while the uppers become cast aluminum. Stabilizer end links are ballpivot type now. Unchanged is the use of bolt-in wheel bearing/hub assemblies.

The most significant change for technicians may be that the alignment adjusters are now on the lower arm—considerably easier to access during service.

Technicians that currently install leveling or lift kits should be aware that Sierra AT4 and Silverado’s equivalent Trailboss models come from the factory with a 2-inch lift that is apparently incompatible with aftermarket spacer and lift kits intended for regular models.

Major changes have occurred in the braking system of these new trucks. The adoption of electro-hydraulic assist for the brakes—with the ABS/ESC/booster unit now under the hood and requiring DOT 4 fluid—is a big change. The reservoir for the brakes now hides below the outboard side of the coolant tank.

Equally noteworthy is the switch to on-caliper electric actuators for the parking brake, with the switch rather incongruously placed on the lower left side of the dash.

Front brakes now feature import-style 4 piston calipers and are equipped with a single wear sensor on the driver’s inboard pad. Technicians should be aware that there is also an estimated brake life readout in the dash that must be reset after friction replacement.

Clever cargo area
Exclusive to GMC is the optional “Multipro” reconfigurable tailgate-within- a-tailgate. The cut-out section can fold down to serve as access or a second load tier, while a flap on it can restrain cargo or serve as a step. Chevy counters with a power closing tailgate—GMC only offers power lowering.

Larger internally, the box now has multiple tie-downs and offers built-in LED lighting and a 110V outlet; in select GMC models the box itself is optionally carbon fibre-plastic composite.

Categories : Mechanical


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