Tom Berg, Truck Editor
Usually we open these articles with a front-corner photo of a truck because that's how we like to look at the vehicle. This time we went with a shot of the Mack TerraPro's cab interior because noticeably increased room for the driver is the main improvement over its successor, known simply as the MR low-cabover.
The TerraPro has 2 inches more space between the seat and the wheel and pedals, which are suspended rather than floor-mounted. This was done by redesigning the dashboard and moving the steering column forward. And the console area of engine cover is lower by about a half a foot. The driver can readily see over the cover, and there's space on top to lay his lunch and for a strapped-down fire extinguisher, among other things. The cover could be made smaller because the new-series MP7 diesel is more compact in height than previous engines.
Mack TerraPro Test Set
Truck: Mack TerraPro MRU613-1120, heavy low-cab-forward, BBC 63 inches w/4.75 bumper extension, main-frame steel rails 3/8- × 13-3/8- × 3-1/4-in., GVWR 80,000 pounds
Engine: MP7-405 Maxidyne, 10.8 liters (659 cubic inches), 405 hp @ 1,500 to 1,900 rpm, 1,480 lbs.-ft. @ 1,100 to 1,300 rpm
Clutch: Eaton CL798 w/15.5-in. ceramic facing
Transmission: Mack T309LR 9-speed
Front axle: Mack FXL20, 20,000-lb. capacity on 20,000-lb. multileafs
Rear axles: Mack S440, 44,000-lb. tandem w/ 4.64 ratio, on Mack SS440 Camelback multileaf
Wheelbase: 235 inches
Tires & wheels: 425/65R22.5 Michelin XTE2 front, 11R22.5 XDE M/S rear, on Alcoa polished aluminum discs
Brakes: Meritor S-cam w/Haldex automatic slack adjusters and Bendix ABS
Fuel tank: 110-gal. polished aluminum, right-side mount
The cab structure itself is no bigger, according to Steve Ginter, Mack's vocational-segment product manager. He showed me around the TerraPro during a visit to Allentown some months ago. Its letter designation is MRU, with U indicating the need to burn ultra-low-sulfur diesel fuel in the engine.
The TerraPro also got a chromed-trimmed grille and, more seriously, is multi-plex wired for modern electronic controls for its EPA-2007 diesel and all accessories. 2010 engines will also be efficiently wired in. It's a thoroughly modern heavy truck even if it doesn't look all that different outside.
What seemed to remain traditional was the ride, but with reason. The bare chassis was set up for a concrete pumper body and without it was much too light for its stiff front and rear suspensions. The frame's main rails had no reinforcement channels, but their height was 13-3/8 inches, adding to the stiffness, which of course becomes necessary when the heavy body is installed and supported. As it was, the chassis was probably driven cross country to a dealer or body manufacturer, and its drive-away operator would've known with every bump in the pavement that this was not a fancy over-the-road tractor.
Of course, the driver's position looks and feels almost unique by truck standards. "Low-cab-forward" means what it says: The cab sits low and somewhat ahead of the engine, so the cover in the middle encloses the radiator, fan and shroud, and forward part of the engine block, which protrudes slightly from the cab's rear.
The new cover is still wide, but there's enough room for the shift lever. Higher, the cover slants inward and then flattens to accommodate a switch panel. The stuff atop the cover introduces a little hemmed-in feeling, but there's still a clear view to the right, through the passenger-door's window at what traffic's out there, and of course what's to the rear through the mirror.
Ahead and through the steering wheel is a pod with the speedometer and tachometer, which are in ready view through the wheel's rim and spokes. The headlight switch is in a small panel to the left, and a larger wing panel houses a pair of gauges and controls for the HVAC system. Instrumentation is sparse, but adequate for this kind of truck.
The shift lever mounts to a stationary pedestal on the floor; the lever stays in place when the cab is tilted, so the lever feels firm and never rubbery. The shift mechanism was new-truck-stiff, but I was able to easily find each gear position in the 9-speed transmission and had little trouble going through the few gears I needed.
With no weight aboard, the 405-horse MP7 diesel felt very peppy and propelled us briskly down the streets. The chassis' long wheelbase required some planning for square right-hand turns, but the smallish steering wheel was fun to spin. A heavy body would settle things down and give the truck an appropriately ponderous feel.
My drive was on streets in the vicinity of Mack's headquarters (soon to be moved to Greensboro, N.C.), where pavement was sometimes smooth and sometimes bowed. I couldn't help thinking that it was ironic that a concrete pumper truck would be subjected to a beating from less-than-par concrete pavement. Maybe the federal Stimulus money will find its way to Allentown and many other northern towns badly in need of street repairs.
So the TerraPro redesign improves the workplace for its driver and makes this tough Mack model more competitive. To be sure, one or two other truck builders offer bigger cabs and sometimes smoother-riding chassis, yet Mack's reputation for ruggedness and longevity makes the MR the most-seen model for this kind of service. TerraPro's improvements will help keep it on top.
