These are good days for Peterbilt. The company is logging record sales numbers, and that includes high volumes for its Model 567 vocational truck. Recently, on a dusty desert track in Gateway Canyon, Colorado, I was given the opportunity to take several commonly spec’d Model 567 trucks through their paces to see why this truck has proven to be such a winner since its launch three years ago.

To begin with, the Model 567 takes essentially everything Peterbilt has learned about trucking over the past 80 years and boiled it down into the company’s take on a quintessential work truck. If you’re a Peterbilt fan, it’s all here: The broad-shouldered stance, the flashy chrome grille topped off with the aggressively subtle sloped hood, all set the tone from outside the truck. Then you climb up into the cab and note the luxurious creature comforts culled from years of refinement on Peterbilt’s family of long-haul tractors.

Since its launch in 2014, Peterbilt hasn’t done much to tweak the Model 567 design beyond a few, minor, under-the-skin changes. Most of these deal with air and electric line routings. What the company has been doing, however, is working closely with suppliers such as Cummins, Eaton, and Allison to enhance the specs fleets can choose from when ordering a truck.

“Vocational applications are tough and amazingly varied,” notes Charlie Cook, Peterbilt’s vocational market segment manager. “We have to make sure that we have a wide array of engines and transmissions available to help our customers meet any challenge that they face.”

The trucks assembled on an isolated, 2-mile-long, Baja race course ringed by mesas and mountains reflected this philosophy, boasting an array of transmissions, suspensions, engines and axle configurations, including the Cummins X15 diesel engine and new, vocational-optimized Eaton UltraShift plus automated gearboxes. “Manual transmissions are still a considerable portion of our vocational sales today,” notes Tony Sablar, vocational marketing manager, Peterbilt. However, “over 50% of our vocational sales today are spec’d with automated transmissions and that trend has accelerated in the past couple of years.”

Behind the Wheel

If you’ve climbed into a Peterbilt cab lately, there are a lot of familiar features awaiting you once you settle behind the wheel of a Model 567. As modern as this truck is, there’s a bit of nostalgia too, as Peterbilt still uses box-style, add-on sleepers for their vocational trucks. It’s a throwback in an age of fully integrated truck cabs. But the Peterbilt argument is sound: They simply feel that a vocational truck will have more value in its second life if a sleeper is not required and can be easily removed to meet a new owner’s needs.

But even if the overall concept is an old one, Peterbilt Model 567 sleepers are thoroughly modern. This includes a solid mount that keeps noise and vibration at a minimum, as well as all the features, luxuries and amenities drivers expect in sleeper appointments.

One of the most important of those features is air conditioning. And given that we were in a near-desert on the Colorado-Utah border, it’s only fair to give a shout-out to the Model 567’s HVAC system, which was working hard to keep the truck editors and our Peterbilt hosts on the healthy side of a heat stroke. Kidding aside, the point stands: Our test drive area was one of the toughest environments in North America to run a vocational truck. And in a place where summertime temperatures in excess of 100 degrees are routine, the performance of a truck’s air conditioning system is of vital importance for driver safety, comfort and productivity. And on this count, the Model 567’s air conditioning delivered in spades. The system delivered a steady stream of ice-cold air to keep the cab comfortable – and it wasn’t necessary to keep the fan cranked up to full blast in order to do so. Moreover, the HVAC in the Model 567 is remarkably quiet.

In fact, the entire cab on the Model 567 is amazingly quiet, considering the brutal terrain we were driving in. Given all the bumps, jars, ruts, hills and air conditioning going on while we twisted and turned our way around the 2-mile course, you’d have to yell to be heard by your passenger in many trucks. But the sound insulation work on the cab by Peterbilt designers is so well done that you don’t have to. Outside noises from the suspension, the road, and powertrain are muted to an impressive degree. And the same holds true for interior features like the HVAC system.

Looking forward from the driver’s seat, you’re greeted with Peterbilt’s usual sweeping, panoramic views over the aggressively sloped front hood. Views to the side of the truck are excellent as well. Rear-view mirror placement is excellent, and Peterbilt engineers deserve a lot of praise for the design of the mirror brackets. Our test track was, as I said, designed as a loop for Baja truck racing. So, naturally, it featured a seemingly endless serious of small hills, ruts, bumps, rocks and inclines. And yet, as bouncy and bumpy as the ride got, the Model 567’s mirrors stayed rock-steady the entire time.

I was able to drive several different powertrain configurations on the course, including Paccar MX-11 and MX-13 and Cummins X15 engines mated to the Allison 4500 RDS-P and 4700 RDS-P automatic transmission as well as vocational Eaton UltraShift automated manual gearboxes. In each instance, the trucks performed exceptionally well.

Because of the off-road course, it was impossible to go much faster than 35 to 40 mph – and then only for very brief distances. So most of my impressions centered on low-end torque and acceleration. Obviously, the Cummins X15 and Paccar MX-13 provide a bit more low-end grunt than the MX-11. But not by much – was a point Charlie Cook was keen to make: Fuel-conscious fleets today can spec an 11L diesel engine. And these engines, when properly mated to the correct automatic or automated manual transmission, give low-end performance that is awfully close to the sort of power the bigger displacement engines deliver.

A final point has to be made about the steering system on the Model 567. Steering and handling is always a feature I key in on when test driving a truck. Nowhere else does a steering system have to step up like it does on a tough, off -oad course with hairpin turns and other sudden twists and turns. In each truck, steering response was crisp and immediate, with no over- or under-steer required. Likewise, the truck instantly went were you wanted it to without trying to wander off if the front tires happened upon a rut they were particularly fond of.

All told, it’s easy to see why Peterbilt is posting record numbers in gaining vocational marketshare these days. They have a solid, comfortable and well thought out design on their hands with the Model 567 that is perfectly happy running in some of the hottest, brutal terrain imaginable.