GMC Sierra towing capacity ranges up to 5,443 kg (12,000 lb) with the 6.2L V8, 3.73 axle and max trailering package, but more common trims typically rate about 4,300–4,500 kg towing capacity (9,500–9,900 lb), and the 4.3L V6 maxes out at 3,266 kg (7,200 lb), claimed best in class for naturally aspirated V6 trucks. Payload in most specs ranges from almost 800 kg to over 950 kg depending on trims, engine, and configuration.
  2014 GMC Sierra. Click image to enlarge |
As mentioned, our first leg was with a trailer hitched, estimated at 3,400 kg (7,500 lb), so by no means taxing the maximum towing capacity, but nonetheless a substantial load that demonstrated the Sierra’s capability. As far as power goes, the 5.3’s 383 lb-ft of torque seemed sufficient for this weight pulling through the rolling hills of southern Alberta heading in the direction of Lethbridge. However, I would not want to add another thousand kilos, as some of the steeper grades had us down in second gear and struggling to maintain speed.
In fact, it was the transmission that most disappointed me – not that it failed in any way, but at certain times, when I attempted to use the manual gear selector to get it down into third or second gear for an incline, it had little or no effect. Tow/haul mode was suitable 98 percent of the time, but I would be a bit concerned about that other two percent if it did not allow me to lock in the specific gear I chose.
The feature that impressed me most, and arguably the most important when towing, was the brakes. The brakes were always smooth and strong, never feeling even taxed by the load, and combined with the trailer sway control always felt that the load was settled and under complete control. GMC Sierras are equipped power assisted ABS disc brakes with 330-mm vented rotors in front (13 in.) and 345 mm rotors in back (13.6 in.).
   2014 GMC Sierra. Click image to enlarge |
Although towing that much weight highlights every imperfection in the road and any bump seems to have an echo, the frame demonstrated little in the way of twist or flex, and eventually I settled in to a comfort zone, enough that we tested the truck’s high-speed stability under load, passing several slow transports and never feeling out of breath at high speeds (and high altitudes). As solid as the chassis is, I found it a little disappointing that GM hasn’t advanced the bar significantly is any area except perhaps powertrain, with the new Ecotec3 range adding direct injection, cylinder deactivation and variable valve timing.
At the end of our towing route, which was just under 200 km and overall a gain in elevation with lots of climbs and descents, the trip computer showed 25.8 L/100 km, which is nothing to write home about, but there’s only so much you can expect under these conditions. We would love to hear from our readers in the comments about the fuel consumption they achieve towing any significant loads.
On the return leg into Calgary, we were no longer saddled with the trailers, and the engine showed its impressive efficiency side. Of course, unburdened, it was also a pleasure to run up the revs and enjoy the power to accelerate and power up hills – I do confess a certain love for V8s.
  2014 GMC Sierra. Click image to enlarge |
Sierra 5.3L V8 4WD models are officially rated by the EPA at 13.0 L/100 km city, 8.7 highway and 11.0 combined. While that 8.7 seems optimistic, we achieved 11.5 L/100 km driving mostly highway and intermediate highway. GM was touting the efficiency of their V6, which rated a not much better than the V8 12.6/9.0/11.0 city/highway/combined in comparable 4WD trim. Why bother? Okay, perhaps this is a good solution for some fleet applications, and if the cost is lower, that speaks for itself. The official ratings are neck and neck with Ram’s 1500 V6/eight-speed transmission combo.
