Mack tricked out this Pinnacle axle forward for the
Ride for Freedom to commemorate America’s fallen heroes.

Yeah, the Mack CH axle-forward has been around a while, but this one has a lot of new stuff going for it, most notably, the company’s new 13-liter MP8 engine. That would be reason enough to take one for a spin, but EPA-’07 has wrought a lot of other changes and improvements upon the product line. This one is almost entirely new from the frame rails up.

Mack is still using its Advantage chassis, but that too underwent a number of modifications to accommodate the new engines — that’s one of the reasons Mack was a little late rolling out its ’07 product. The cab is what Mack used to call its heavy-duty cab, a sturdier version of the standard cab. That’s now the standard cab.

The leaner profile of the MP-series engines has improved under-hood air management considerably. They are 14 inches narrower than the ASET engines, and they sit lower and farther back in the frame, which improves airflow under the hood. A new radiator mounting system has allowed Mack to tailor the rad to the operation and vehicle configuration — using taller, shorter, or wider cooling modules as required.

According to Mack’s powertrain marketing manager, Dave McKenna, “high underhood air temperatures are no longer an issue.”

Techs will like the new engine mounting position for ease of maintenance. You can easily see pavement between the engine and frame rails, and more of the maintenance points are more easily accessible.

Our test truck had a Mack 18 speed, officially known as the T318LR — the newest generation of an established line of gearboxes. It’s a close-ratio (18 percent average steps) triple-countershaft box with 18 forward and four reverse gears. Some say the triple-countershaft design makes for sluggish shifting, but I’d respectfully disagree. The upgrade in the design has moved the gear gates closer together, so the stick throw is shorter and tighter. As well, the shift rail profile has been improved and the sliding clutches have been redesigned with finer teeth for more load bearing surface and better gear meshing. In other words, if you mis-time a shift, the stick won’t buck like it used to. And with three countershafts, it’s unlikely to grow sloppy as it ages.

This box was rated at 1,800 lb ft of torque, and the MP8 produces 1,660, so it’s well within the envelope. In top gear, you’ve got a tall 0.71 overdrive ratio, so it’s kind to your pocketbook as well.

Out On the Road:

If you’re looking for an axle-forward tractor without a gigantic nose, this might be your truck. Its modest 116-in. BBC makes it very maneuverable, and with its 50-degree wheel-cut, there’s almost nowhere you couldn’t put this truck. Even with its 70-in. sleeper, the wheelbase was only 243 in. –legal for Canada.

And it’s light on its feet. Axle-weighed bob-tail, half full of fuel it was just 18,120 lb. The steer axle was 9,480 lb, leaving a lot of room to slide payload forward. With a 48-ft wagon full of concrete block grossing just over 76,000 lb, I steered the truck out of Mack World Headquarters in Allentown, Penn, and headed west on I-78 for Harrisburg.

The fully multiplexed dash is easy on the eyes.

On most of the hills, only a split was required of the top gear. The engine lugged confidently down to 1,100 many times and kept on pulling — I let it drift even lower a few times, and while the torque starts to drop off a little below 1,000, it just grunts away.

Maxicruise engines should be run between 1,450 and 1,500 rpm at cruise speed, Mack says, so you’ll have adequate horsepower at cruise for acceptable gradeability and acceleration. This truck was geared for 1,500 at 65 mph, 1,420 at 62 (100 km/h). With 485 horsepower and 1,660 lb ft of torque, I’d say you could get away with pulling a tridem just about anywhere in Canada, and even B-Trains in many parts of the country, though I might spec a different rear end with a Super B. Tandem/tandem ops? A walk in the park for the MP8.

The engine-transmission combination was very complimentary — another feather in the hat of the integrated powertrain. Loaded light like I was (in Canadian terms) the 18-speed was overkill, but the top end of Mack’s Maxitorque T313LR 13-speed is identical, so the results would have been the same.

At the end of the day, what’s the driver-to-truck interface but working the pedals and the stick and hanging on to the wheel? This CHU 613 axle-forward Pinnacle shone on every count. I didn’t feel the least bit worn out at the end of a day that included a lot of shifting and steering. Interstates are fine, but they don’t challenge a truck and driver the way some of Pennsylvania’s lesser known highways do, and that’s where I like to test a truck.

It was darned quiet too, registering no more than 68 dB on my sound meter under a heavy pull or with the engine brake (Mack calls it a Power-Leash) on. At cruise, it read 67, just a point higher than the much-touted ProStar and Cascadia.

A new floor insulation is at least partially responsible for the quiet. It’s a polyurethane material that’s supposed to last 10 times longer than previous material. And the clever engineers over at Mack have designed the flooring with removable but watertight panels in the foot wells and over the transmission. They can be switched out as they wear, and the transmission panel can be lifted out for easy access to the top of the transmission.

Overall impressions? It’s a fine choice for a value-conscious fleet or owner-op in a weight sensitive application.

All of Mack’s Pinnacle series on-highway trucks are now available with full side skirts and side fairings, and Mack has made the Bendix roll-stability system a non-deletable standard feature on all trucks, adding immeasurably to the overall safety of the vehicle.

Mack may have had issues with the ASET engines, but they’re out of production now, and this new cab, chassis, engine, and transmission line is sure to please. If Mack isn’t on short list for your next truck, you owe it to yourself to check one out.