Diesels are a big deal, and getting bigger. A diesel has always been a truck's single most complex and expensive component, and that's even truer of cleaner-burning engines due out in January. Developing the diesels and preparing trucks for them has been time-consuming and costly for manufacturers, so much so that Peterbilt Motors renamed most of its vocational and highway models to mark the changeover.
One is this Model 365, which is replacing the 357 that's long been a popular dump and mixer chassis in many markets. The 365, complete with a Kimbel mixer body, was available for a drive in Denton, Texas, home of Peterbilt's headquarters and one of its two plants, and I journeyed there on a hot day in August to check it out.
What I found was that the 365 looks and drives like a 357 because, except for the 2007 engine and changes related to it, it's pretty much the same truck. It's got the same 370-series aluminum cab, steeply sloped hood, flat fenders and headlight pods mounted to the hood. The 365 can be ordered with either a forward-set or setback steer axle to maximize loading in bridge-formula or axle-weight states.
The 365 has a medium-length nose to house 9- to 13-liter engines from Cummins and Caterpillar. This particular truck had an 11-liter Cummins ISM, which many ready mix companies choose for its combination of low weight and good performance. A companion truck in Peterbilt's new vocational lineup is the 367, with a long nose to take 15-liter engines.
Also under the 365's hood was a larger cooling system that includes a 1,438-square-inch core, about 30 percent bigger than before, which will handle the extra heat that the engine will shrug off under some circumstances. In the 365's exhaust stack was an after-treatment device consisting of an oxygen catalyst and diesel particulate filter. It looks like a big muffler with wires running to it.
It does act as a muffler, but its primary job is to scrub out any oxides of nitrogen (NOx) and soot that the new engine can't deal with.
Periodically the device's sensors will tell the engine's electronic controls that the filter is loaded with ash (from motor oil, not combustion) and they will trigger a regeneration. A small amount of fuel will burn off the ash, causing a high heat (up to 1,200 degrees F), that will largely be contained in the double-walled device. It's mounted high and shielded, so shouldn't burn anybody.
Did I mention heat? The temperature readout on the instrument panel said "104 F" as I was leaving the plant premises. I cranked up the air conditioning and left it on when I ventured out to shoot pictures. This violated my own anti-idling rule, and I'm sorry, but I wanted the cab cool for when I jumped back in.
While scurrying about with the camera I realized that I wasn't smelling any exhaust odor. I mean, there was absolutely no diesel aroma, or stink, depending on your point of view, or smell. The new '07 emissions controls had so seriously pinched down NOx — the source of the characteristic smell of diesel exhaust — that the smell is gone. There was absolutely no smoke coming out the stack, either. That should please a lot of people, including drivers and crews at pour sites.
The 365's big, wide hood took a good yank to tilt forward, and it locks in place so wind can't blow it back down until a sliding lever is released. On most trucks the lock is on the curb side, where I unsuccessfully sought it until Derek Smith, Peterbilt's public relations manager, pointed out that the lock's on the left side of this truck.
The 350-hp Cummins sounded nice and behaved well. It didn't have a lot of guts, but it was brand new and far from broken in: The odometer showed only 29 miles when I left the Denton plant. The mixer drum was empty so I skip-shifted through the 11-speed Fuller "LL" and never used its low-low ratios. The tranny shifted smoothly if I remembered to move the stick quickly, which you must do with most modern engines.
The drum was empty because this is one of Peterbilt's 2006 show trucks, Smith explained. No one wanted to risk scratching the funnel with crushed rock or some other ballast material, as they had last year with a 357 mixer that I drove.
From the plant, I headed to Interstate 35 and swung north, going as far as Sanger, a dusty small town with no vacation villas but enough streets with bruised concrete and asphalt to give a good workout to mechanical suspensions over the axles and air bags under the cab and beneath the seat. The ride was pretty good, considering the axle suspensions' high ratings (20,000 and 46,000 pounds) and that empty drum.
Big "duplex" tires on the steer axle limited wheel cut and made for a wide turning circle, but it wasn't bad if I cranked the wheel early in a turn, especially while backing up. TRW dual power assist removes the work in hard turns, but also introduces some vagueness at highway speeds — normal for an extra heavy-duty front axle.
Peterbilt's stout cab sits high off the pavement on the 365 chassis, as it does on a 357. It's narrow by some comparisons, but is roomy enough for construction duty, or is if the driver doesn't pack in a lot of gear. There's enough space in the cab for two seats, including a low-back passenger seat that squeaked annoyingly while underway.
Between the seats was a big console with switches and other controls for the mixer. There were two holes where the pusher-axle switches will go, and the rear booster axle was disabled. So I couldn't drop the auxiliary axles if I had wanted to, and the truck was a 10-wheeler for this trip.
Interiors were redesigned last year for the 357 and are carried through to the 365. This truck had the base ProBilt interior, which looked nice in grey and is practical, though its Vinyl seat covers are sticky.
From the high-backed driver's seat there was a good view through the windshield and over the sloping hood. The hood is wide and there was a blind spot alongside the right-front wheel, but I never ran over anything I didn't want to. The view in other directions is excellent. There's a big window on the rear wall, neat curved corner windows and a peep window in the passenger door. This truck had motorized Moto Mirrors, but they were set just-so, and I never needed to remotely adjust them.
On the tall, wide instrument panel were two rocker switches for the cruise control, which I used while zipping along I-35. I usually cruised at 60 mph, which in top gear was a little over 1,700 rpm on the tachometer — just where the engine should be in a vocational truck, according to Cummins. For me, 60 would be fast enough with nine or 10 yards of concrete aboard and all axles down, but the truck's overall gearing would let a guy in a hurry make even better headway.
So, this is how Peterbilt's mixer customers will zip into the future, in a truck that has a lot of familiar features along with the necessary advances to meet the new emissions standards. Do the changes add up enough to justify the new model number? If I had been among the Peterbilt people who worked so hard to get this truck to market with those January '07 diesels, I'd say yes.
If I were a buyer who will be asked to spend thousands of extra dollars over a predecessor model to acquire one, I might feel my investment more than paid for a higher model number. If I were the driver of this 365, I think I'd enjoy going to work in it. And with the cleaner burning engine, I'd definitely appreciate breathing easier.