December 2007/January 2008
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Under the Hood With '08 Trucks

There are few outward signs of the many changes that have occurred under the hood and chassis of medium-duty trucks, but the changeover to new diesel emission-reduction hardware is complete with the current models.

By Jim Galligan

The 2008 model-year trucks don't look all that different, but last year at this time only some medium-duty truck makers had introduced their 2007-compliant models. Now, all new diesel-powered trucks come with the exhaust systems needed to meet the diesel emission standards that went into effect this past January.

While all diesel trucks must meet the same emission standards and are using essentially the same components, there are many differences in how these changes are engineered from manufacturer to manufacturer, even from model to model. All the 2007-compliant trucks include basically the same components, including new exhaust systems and diesel particulate filters.

The diesel emission-reduction systems operate in much the same way, too. The exhaust feeds into the DPF, which traps particulate matter in the exhaust. Over time - which could be a matter of hours in some operations, the particulate matter, or soot, must be cleaned out of the DPF. This "regeneration" process is accomplished by raising the temperature of the exhaust to about 1,200 degrees Fahrenheit - depending on the system - and burning off the collected soot. Sensors in the exhaust system will monitor the pressure in the DPF and start the regeneration process when a pressure buildup indicates the filter is clogged.

Beyond those basics, the differences multiply. Begin with the regeneration process. Some truck makers enable the operator to override the automatic system for a period of time, while in other trucks the process is totally automatic and the operator has no control over regeneration. There also are differences in how the components are packaged, where the exhaust systems are routed and which substrate material is used in the filters.

The Ripple Effect

The addition of these emission-controlling systems forced other changes under the hoods, including larger exhaust gas recirculation and cooling systems. All manufacturers had to deal with higher operating temperatures. One side effect of the higher engine temperatures is higher nitrogen oxide levels. Engine manufacturers enlarged exhaust gas recirculation systems, as well as radiators, to lower temperatures and keep NOx emission levels under the current standards.

Most - but not all - trucks are using larger, more expensive electronically controlled variable geometry turbochargers for better fuel-economy control. There are changes in some chassis, as well. Some manufacturers lowered the engine a few inches to allow room for the enlarged EGR systems and cooling capacity. Some dropped the radiator between the frame rails to make room for the larger cooling system. That, in turn, affects the front-mounted power takeoff connections in some models.

Several truck makers shifted the under-chassis wiring, partly to improve routing and connections for upfitters, but also to keep the wires away from the hotter exhaust systems.

Get the picture? All in all, there are too many variations among the models to list them here individually. Most of these differences will mean little to the typical straight-truck buyer, but those using special or customized bodies may see a change from previous models. Contact the vehicle manufacturer for details about its emission-control system.

The changeover to the new emission standards gave manufacturers an opportunity to upgrade models. Isuzu introduced the first upgrade in its N-Series trucks since 1995, and Mitsubishi Fuso upgraded its FE models. Beyond those changes, there are new or significantly upgraded models from Dodge, Ford, General Motors, Kenworth, Peterbilt and Sterling.

Following is a review of the current medium-duty (Classes 3-7) truck models. We will review light-duty trucks and vans in the December/January issue of LIGHT & MEDIUM TRUCK.


Dodge added the Dodge Ram 4500 and 5500 chassis cabs to its commercial truck lineup for 2008.

Both truck models are powered by the Cummins 6.7-liter turbo diesel rated at 305 horsepower and up to 610 foot-pounds of torque. A 6-speed manual transmission with power-takeoff capability is standard, but a 6-speed automatic also is available.

The 4500 almost qualifies as a Class 5 truck, with a gross vehicle weight rating up to 16,500 pounds and a 5,000-pound payload. The 5500 is rated at 19,500 pounds gross vehicle weight and will be able to handle up to an 11,000-pound payload.

The C-channel frame for the 4500 and 5500 is a thicker gauge (50,000 pounds per square inch) than the Class 3 3500 chassis cab introduced last year, but it, too, is 34 inches wide and will accommodate most bodies.

The truck is available in four cab-axle lengths (60-, 84-, 108- and 120 inches) and with dual-rear wheels.

The trucks can be spec'd in three trim levels, starting with the base ST, the SLT and the top-of-the-line Laramie. Suggested retail prices for the trucks range between $34,050 for the 4500 ST regular cab 4x2 and $50,700 for the 5500 Laramie quad cab 4x4.

Ford Motor Co.

Ford upgraded its F-350, -450 and -550 Super Duty series for 2008 with, in some cases, new chassis and suspensions as well as new features across all the trucks.

The 6.4-liter Power Stroke V-8 is still the only diesel offered. The engine is rated at 350 hp and 650 foot-pounds of torque. Gasoline options include the 5.4-liter V-8 (300 hp/365 foot-pounds) or the 6.8-liter V-10 (362 hp/467 foot-pounds).

According to Ford, more than 90% of its Super Duty customers tow, so the company developed a factory-built F-450 pickup with a maximum towing capacity of more than 24,000 pounds and a maximum payload of more than 6,000 pounds. Ford added a new rear leaf-spring suspension along with the radius arm front suspension from the F-450 chassis cab.

A new feature is an optional rearview camera system. The camera is mounted in the tailgate and is activated when the vehicle is shifted into reverse. The tailgate can be removed without having to unhook or unplug the camera.

F-650, F-750

Ford expanded the component options when it introduced the updated versions of these medium-duty models a few years ago. The trucks are available in regular, super or crew-cab configurations as a straight truck or tractor with 38 wheelbase combinations, nine frame strengths, five multileaf and three air suspension systems.

Engine choices include the upgraded 6.7-liter Cummins I-6 with its new power ratings or the 7.2-liter I-6 Caterpillar C-7. The Allison 2000 series automatic transmission series was upgraded to handle higher torque engine outputs and can replace the higher-priced 3000 series in more applications, a company official said.

The company has added a 14,000-pound steer axle and is now using Hankook as a standard tire supplier.

2008 LCF

The LCF (low-cab-forward) was introduced in 2005 and there are few changes. The truck has a longer minimum wheelbase (115 inches). Power windows and door locks now are standard, as are cloth seats and an integrated head restraint for the center seat back.

The only available engine is the 4.5-liter V-6 diesel from International Truck and Engine Corp. It provides 200 hp and 440 pound-feet of torque. It is matched with the TorqShift automatic.

Freightliner Trucks

Freightliner's Business Class M2 trucks, the 106 and 112, are available either as a truck or tractor or with varied vocational options, such as front-mounted PTO or front frame extensions in the case of the 106V and 112V truck versions.

The 106 model comes standard with the MBE 900 engine with power ratings from 170 hp to 350 hp. Depending on the components, it can be spec'd with Eaton-Fuller manual transmissions, Eaton Fuller AutoShift and UltraShift; Allison automatics; or Mercedes-Benz automated manual transmissions.

The 112 performs more like a "Baby 8" with GVWR up to 66,000 pounds when spec'd for heavier work. The main power is the MBE 4000 engine, with ratings from 350 hp to 450 hp and up to 1,450 foot-pounds of torque. Freightliner also offers the Cummins ISB, ISC and Caterpillar C13 engines in the M2 models.

New turbocharger design improves responsiveness while reducing the amount of fuel required for acceleration, according to the company. Standard engine wiring and lighting connectors eliminate the need for splicing during most upfitting and body work. Cab configurations include a day cab, a 26-inch extended cab and a 48-inch crew cab.

Freightliner Custom Chassis

The Class 4 MT45 carries a GVWR between 14,500 and 19,000 pounds, accepts bodies up to 22 feet and handles payloads up to 10,000 pounds.

The Class 5 MT55 carries a GVWR between 20,000 and 30,000 pounds and handles payloads up to 19,000 pounds.

The standard power for both is the Cummins ISB, rated at 200 hp and 520 foot-pounds of torque. The Allison 1000 or 2100 HS automatic transmissions are standard, depending on the chassis, with various other Allison specs optional.

A multiplex wiring instrument cluster is new, and a vehicle information display monitors engine diagnostics and 20 chassis functions. The operator station has been enlarged to provide permanent mounting of wiring, hand brake and cables.

General Motors (Chevrolet/GMC)

The light-medium Class 4 (4500 model) and Class 5 (5500) are available in regular or crew-cab configurations with both gasoline and diesel engines. The 8.1-liter Vortec V-8 gas engine is rated at 325 hp and 450 foot-pounds of torque. The 6.6-liter V-8 diesel is available in ratings of 300 hp/530 foot-pounds and 330 hp/620 foot-pounds. The Allison 1000 6-speed automatic is the standard transmission.

The Classes 6-8 C6500/7500/8500 trucks have two diesel options: the Isuzu 6H 7.8-liter diesel (215-300 hp/560-860 foot-pounds) or the Caterpillar C7 (207-250 hp/520-800 foot-pounds), as well as the 8.1-liter gas engine. All are matched to a variety of Allison automatics or Eaton-Fuller manual transmissions.

GM added a tandem air suspension rated at 40,000 pounds and a tandem rubber suspension rated at 46,000 pounds for 2008.

LCF Series

The light medium (Classes 3-5) W-Series low-cab-forward truck gets an all-new cab and engine for 2008.

The new Isuzu-built 5.2-liter, 4-cylinder diesel is rated at 205 hp and 441 foot-pounds of torque. The W Series is also available with the 6.0-liter V-8 gas engine rated at 325 hp and 360 foot-pounds. The standard transmission is the Aisin 6-speed double-overdrive automatic.

The larger T-Series (Classes 6-8) adds a 300 hp/860 foot-pound torque rating to the 7.8-liter Isuzu turbo diesel engine, the only engine offered. Also new for 2008 are the Allison 2200, 2500 and 2550 6-speed automatic transmissions. An AM/FM radio/CD player is standard.

Hino Trucks

Hino offers models ranging from the 14,050-pound GVW Class 4 145 to the 33,000-pound GVW Class 7 338, available as either truck or tractor.

There are few changes to the cabs. A new information display among the gauges provides the driver with the status of the emission system as well as mileage and maintenance intervals. New standard features also include a heated Davco fuel filter, LED marker lights and an engine glow plug. An exhaust brake is optional.

The Hino 4-cylinder J05D-TF diesel engine, rated at 175 hp and 376 foot-pounds of torque, is standard on the 145, 165 and 185 models. The standard transmissions are the Aisin 4-speed automatic in the 145 and the Eaton 5-speed manual with synchromesh in the 165 and 185. The Allison 1000 5-speed automatic is optional with the 165 and 185.

The 6-cylinder J08E diesel comes with ratings of 220 hp and 520 foot-pounds of torque (for the 238 to 268A models) and 260 hp/585 foot-pounds for the 338 truck and tractor models. The standard transmission choices include the Allison 2200 5-speed automatic for the 238 and 258, the Eaton 6-speed manual with synchromesh for the 268 and 338 (standard) or an optional Allison (2200, 2300) 5-speed automatic.

International Truck and Engine Corp.

There are no significant metal changes in the medium models. International dropped its traditional numerical truck and engine model names in favor of brand names intended to better indicate their applications. The Durastar replaces the 4100-4400 medium-duty series and the Citystar is the low-cab-forward model. The other brands include the Paystar (severe service 5500, 5600, 5900), the Workstar (7300-7700), Transtar (8500, 8600) and the Prostar Class 8 road tractor.

The vehicles themselves are carryovers from last year. The Durastar 4300, for example, is powered by the Maxxforce DT (formerly DT 466) with power offerings of 210 hp or 255 hp (560, 660 foot-pounds, respectively) with either the Eaton manual or Allison 2000 automatic transmissions.

The severe service Workstar received a new hood to accommodate the '07 emission package. It maintains a front engine PTO without affecting the radiator, company officials said.

The Citystar (low-cab-forward) model arrived on the market two years ago. The truck, a sister to the Ford LCF, is powered by International's Maxxforce 5 (formerly VT 275), the 4.5-liter V-6 diesel rated at 200 hp matched with the Ford 5-speed automatic transmission.

Isuzu Trucks

Isuzu has updated its best-selling light-medium N-Series model. The truck is available with either a gasoline or diesel engine and now includes a long-wheelbase option as well as a gasoline-powered crew cab.

A larger cab has more side-to-side and back-to-front room than the previous version. The cab also includes a new dashboard layout with new gauges and warning lamps, telescoping steering wheel, a power outlet and more storage space. An electronic brake force distribution system monitors wheel activity and automatically adjusts braking at different wheels to improve stability.

Standard power comes from the 4-cylinder 5.2-liter Isuzu diesel with ratings of 205 hp and 441 foot-pounds of torque - increases of 8% and 14%, respectively, over the previous ratings. Isuzu also offers the GM-built 6.0-liter V-8 gasoline engine in the NPR and NPR HD models. This latest version is rated at 325 hp - 25 more than previously - and 360 foot-pounds of torque.

The addition of two longer wheelbases - 200 and 212 inches - will let users spec bodies up to 24 feet.


There were no physical changes in the company's larger F-Series. The extended service coverage on the Allison 2200 HS and 2500 HS automatic transmissions was increased to four years/unlimited mileage with factory-fill TranSynd transmission fluid. Eaton Fuller 6-, 9- and 10-speed manual transmissions are also available.

Kenworth Trucks

Kenworth Truck Co. added the Class 7 T370, the Class 6 T270 conventional and the Class 6 K260 low-cab-forward to its midrange truck lineup.

The T370 conventional is available as a tractor or a straight truck with single or tandem axles. It is offered with the Paccar PX-6 engine rated up to 325 hp and 750 foot-pounds of torque, or the Paccar PX-8 (330 hp/1,000 foot-pounds). The PX-8 also has a 360 hp rating for emergency vehicles. Customers can choose manual or automatic transmissions and air or hydraulic brakes.

The T270 is available as a straight truck with a low-profile chassis with 19.5-inch wheels and tires. It also uses the PX-6, and customers can choose from manual or automatic transmissions. Standard features include power door locks, passenger-side electric windows (optional on the driver's side), and DayLite doors with peeper window.

LCF Model

The K260 is based on the DAF LF55, Paccar's LCF model in Europe. The truck is powered by a 5.9-liter diesel rated at 220 hp and 600 foot-pounds of torque. It is currently available with a 6-speed manual transmission, air or mechanical rear suspension and front and rear air disc brakes.

Mitsubishi Fuso

After a two-year absence, Mitsubishi Fuso is reintroducing its Class 3 FE model, the FE125, with 12,500-pound GVWR. The model was held out of U.S. distribution until the onboard diagnostic system, which is required for vehicles under 14,000 pounds GVWR with the new emission-compliant engines, could be added.

The engine is the 4-cylinder 4M50 diesel from Mitsubishi rated at 185 hp and 391 foot-pounds of torque. The transmission is an Aisin 6-speed automatic. The truck is available with three wheelbases: 114.6-, 134.3- and 152.4-inches. Features include cruise control, a programmable PTO, an on-off switchable exhaust brake and four-wheel hydraulic disc brakes.

The FE145 model gets a new 176-inch wheelbase and can now accommodate bodies up to 20 feet long.

The FE180 also gets a longer wheelbase option - 189.4-inches - and now can carry bodies up to 22-feet long. A Mitsubishi 6-speed manual transmission also is available in the FE180 in addition to the standard Aisin automatic.

FK Models

The FK and FM models will have their first major redesign since 1995.

Peterbilt Motors

Peterbilt introduced the Model 325 earlier this year, the company's first Class 5 conventional truck. At its media introduction, company officials said the truck was designed for recovery and towing, lease/rental, pickup and delivery and business services such as parcel delivery, landscaping and construction.

The truck is rated at 19,500 pounds. The only engine offered is the Paccar PX-6, a Cummins-built I-6 diesel with horsepower ratings up to 300 HP and 620 foot-pounds of torque.

The Model 325 has standard front and rear hydraulic disc brakes with ABS and an Eaton-fuller 6-speed manual transmission. Allison automatics are optional.

330, 335

Peterbilt's core medium-duty models, the Class 7 335 and Class 6 330, remain little changed. The 335, available as either a straight truck or tractor, can be ordered with the 6.7 PX-6 or the 8.3L PX-8 engines, the latter with ratings from 240 to 330 hp and a torque range from 600- to 1,000 foot-pounds. The 330 truck model uses the PX-6 engine.


Peterbilt's other midrange truck model is the 220 LCF (210 as a non-CDL Class 6 model). The truck is powered by the Paccar 5.9-liter diesel rated at 220 hp and 600 foot-pounds of torque.

The doors open 90 degrees and the steps are mounted low for easy entry and exit. Front-axle ABS disc brakes are standard.

Only about 100 of these models, imported from Paccar's European DAF subsidiary, were scheduled for delivery this year, but the number will increase substantially in 2008, company officials have said.

Sterling Trucks

Of the varied truck brands in the DaimlerChrysler AG family, Sterling Trucks has been the most aggressive in expanding its product line by borrowing models from other family members.

Last year, Sterling added the Model 360, a rebadged version of the Mitsubishi Fuso LCF in the Classes 4 and 5 weight ranges. For 2008, Sterling is adding a Class 3 version.

The Class 3 360 comes with a GVWR of 12,500 pounds. The truck is powered by a 4-cylinder Mitsubishi diesel rated at 185 hp, a 10-hp increase from last year.

The frame has been lowered about 2 inches to improve cooling under the chassis and around the emission-controlling exhaust system.

The company added cruise control as standard for 2008. The cruise control also can be used to limit top speed and accelerate the engine during stationary PTO applications. Air conditioning and automatic transmission are also standard. The Class 5 LCF 360 adds a 189-inch wheelbase to its lineup.


Sterling also introduced the Bullet this year, a rebadged version of the Dodge Ram 4500/5500 cab chassis. Production is scheduled to begin this fall. Company officials said the pending sale of the Chrysler vehicle group by Sterling's parent company, DaimlerChrysler AG, would not affect production or delivery plans.

The Bullet has maximum GVWR of 16,500 pounds (Class 4) and 19,500 pounds (Class 5), with a maximum gross combination weight rating of 26,000 pounds. It is powered by the Cummins 6.7-liter ISB diesel at 305 hp and 610 foot-pounds of torque. Transmission options include a 6-speed manual or 6-speed automatic.

The truck will be sold through Sterling dealers specializing in light commercial vehicles, company officials said.


The midrange (Classes 5-7) Acterra uses the Cummins ISB as standard power. The Mercedes-Benz MBE 900 is a common option for most applications, while the Cummins ISC, with ratings up to 350 hp for fire, emergency or recreational vehicle applications, is also available. Transmissions include Eaton and MB for manuals, and Eaton and Allison for automatics.

UD/Nissan Diesel

Nissan Diesel offers low-cab-forward models from Classes 4 to 7, beginning with the UD1400 with a GVWR of 14,250 pounds, up to the UD3300 with a GVWR of 32,900 pounds. There are no significant changes in design. The 1400 and Class 5 1800CS (city service) are powered by a 4-cylinder MD-175 diesel rated at 175 hp and 376 foot-pounds of torque. The remaining units, including the 1800HD (heavy duty) use the 6-cylinder MD-230, rated at 230 hp and 506 foot-pounds. The engines and the emission-compliant exhaust systems both are supplied by Hino.

For transmissions, the Aisin 4-speed automatic is the only choice in the 1400. The Nissan Diesel 6-speed manual is standard in all other models with either the Aisin (1800 CS) or Allison 5-speed automatics as options.

Workhorse Custom Chassis

Workhorse Custom Chassis expanded its strip chassis choices with the W62, a model with weight ratings of 19,500 pounds and 23,500 pounds and a choice of either gasoline or diesel power. The company also announced the introduction of a hybrid chassis. WCC is a subsidiary of Navistar International.

The W62 will use GM's 8.1-liter V-8 gasoline engine (310 hp/455 foot-pounds). The standard transmission will be a 5-speed Allison automatic, either the 1000HS or 2000HS, depending on the configuration, the company said.

The diesel engine will be the MaxxForce 5, a 4.5-liter V-6 built by International. The W62 is available in five wheelbase lengths ranging from 157 inches to 218 inches. Chassis features include 4-wheel Meritor Quadraulic disc brakes, Wabco 4-channel anti-lock brake system, cruise control, tilt steering wheel and 225/70 19.5-inch standard tires.

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