This article originally published in Issue 52 of the Turbo Diesel Register.

Truckin' Through the Internet

2007 Diesel Cab and Chassis Introduction

by Robert Patton and Steve St. Laurent

Dateline: March 1, 2006
Location: Atlanta, Georgia, at the National Truck Equipment Association Convention

Dodge’s entry with their Third Generation truck into the commercial pickup market was four-years in the making. Sure, you could purchase a 2500 or 3500 truck, remove the truck’s bed and upfit it with a service body. But, a true, easy-to-configure, commercial truck was not in their product line-up.

When I first read about the cab and chassis introduction, I was not inspired. Then rumbling on the internet (hence, coverage of the introduction in this column) revealed that the cab and chasses would have as its powerplant a new Cummins 6.7 liter engine. Now the show was a must-see event. The NTEA show was held in my hometown, so attendance was easy. I called TDR website guru, Steve St. Laurent, and asked if he could make it to the show with his website video camera in tow. The affirmative “yes!” and I made arrangements for attendance. The show dates conflicted with the publishing of this issue as proof copies had already been sent. So, overlook the typos, grammatical errors and misspellings you may see. Enjoy reading about the cab and chassis introduction as well as the Cummins 6.7 liter engine that will power our 2500/3500 series trucks effective 1/1/07 as new emissions legislation numbers have to be met. I’ll turn the writing over to Steve…

The TDR Editor and I attended the 2006 NTEA work truck show in Atlanta, Georgia, to bring you information from the unveiling of the new 2007 Dodge Ram 3500 Chassis Cab.

As I usually do, I video taped the press conference. TDR members can view the video at the TDR website (www.tdr1.com). I have also included PDF files of the complete press kit as given to us by Dodge. We spent about 30 minutes talking with Scott Kunselman, Chief Engineer for the Dodge Ram, and about an hour with Patrick Shea, Cummins Technical Advisor for Light Duty Automotive, to get information for you on the new trucks as well as the the new engine and transmission.

Starting with the chassis the rear frame rails are upfit-friendly with an industry standard, 34-inch, frame rail spacing, as well as something that is unique to the market segment, flat, obstruction-free frame rails. Also an exclusive: all chassis components are below the frame surface, providing versatility for virtually any upfit application. Here are a few photographs of the rear bed rails. I’ve also included a picture of the Ford chassis cab frame for comparison. As you can see on the Ford cab, the overload perches sit above the frame rails.

The truck is available in both regular cab and Quad Cab configurations. The regular cab can be purchased with a 60-inch or an 84-inch cab-to-rear axle length. The Quad Cab is only available with a 60-inch cab-to-rear axle length. The 84-inch cab-to-axle models are only available in a dual rear wheel configuration.

Here is a chart of dimensions for the different models:

2007 DODGE Ram 3500 Chassis Cab

FORD Chassis Cab

Axles on the new truck are the same American Axle units as supplied on the current Ram 3500 except that the track on the dual rear wheel models is narrower. It is available as both an SRW and a DRW truck. The available rear end ratios are 3.73 and 4.10 with the six-speed manual. Only the 4.10 is available with the new Aisin A568RC, six-speed automatic. The two-wheel drive model has a solid beam front axle with a five link coil spring front suspension just like the four-wheel drive models. Both trucks have a recirculating ball steering system. The GVWR for the SRW models is 10,200 pounds with the DRW models coming in at 12,500 pounds. GCVWR’s range from 21,000 to 23,000 pounds.

The AS68RC is a big transmission.

Cutaway view of the Aisin torque converter.

Big news is happening with transmissions. The standard transmission is the existing G56 six-speed manual with its .74 ratio overdrive and available 3.73 or 4.10 rear end gears. The optional transmission is a six-speed Aisin AS68RC automatic with a .63 ratio overdrive and 4.10 rear end gears. I’ve included pictures of the cutaway transmission that was on display. As you can see in the pictures, the torque convertor is a multiple disc lockup unit. It is rated for exhaust brake usage and is a fully electronically controlled transmission. We asked if this transmission was going to be used in the regular 2500 and 3500 trucks and were told that the ‘07 model will continue with the 48RE.

The engine is an all new 6.7 liter Cummins Turbo Diesel that will meet the 1/1/2007 emissions regulations and produces 305 horsepower at 3,000 rpm and 610 lb-ft of torque at 1,600 rpm. This is not the existing European 6.7 liter Cummins which is a long stroke design. The existing European 6.7 liter was a stroked 5.9 with a bore of 102mm, same as with the existing 5.9. The 2007 Dodge engine has a bore of 107mm and a stroke of 124mm. To meet the new emissions regulations they will use cooled EGR along with a diesel particulate filter, an oxidation catalyst, a variable geometry turbo, and a new controlled sealed crankcase system. This engine is a lot more complicated than the existing design with many more sensors and a much larger ECM to monitor them. For instance, the ECM has 10,000 parameters in it.

The turbo is a Holset variable geometry turbo that uses fixed vanes and a sliding plate to provide the variable geometry. It is actuated by an electric valve. Durability was of primary concern to Cummins engineers. When they looked at variable vane turbos they did not like what they saw. They felt that this Holset design was much simpler and more durable. The center section of the turbo is now water cooled. With the variable geometry turbo it can now be used as an exhaust brake. You can order the controls as a factory option to make the turbo function as an exhaust brake. All of the mechanicals are there in the turbo, but it needs the controls to function. It is quoted as being able to provide 35% more braking than the existing butterfly valve exhaust brakes. The switch for the exhaust brake will be integrated into the center stack of the instrument panel in the same area as the seat heater controls.

Yes, the turbo is watercooled.

Look closely and you can see the variable geometry on the new Cummins 6.7 liter engine.

Again, this system is much more complicated than the existing high-pressure, common-rail engine. However, it has been used by Cummins since 2002 with 300,000 engines currently in use and over 30 billion miles on the road.

In the exhaust system there is a self cleaning diesel particulate filter (DPF), an oxidation catalyst, and a muffler. The muffler is not part of the emissions control system and can be removed without violating emissions compliance. As a part of the DPF system the ECM monitors three temperature sensors and change in pressure to monitor the state of the filter. To self-clean the DPF system, it raises exhaust gas temperatures (within a window) by manipulating the air fuel ratio. This is done thru a number of methods—some of which include an injection of fuel to ignite inside the DPF, the variable geometry turbo, and an intake flap mounted sjust prior to the intake air horn. The emissions system is designed for a government certified 185,000 mile life and remains within the 2007 emissions specs.

Diesel Particulate Filter

The exhaust recirculation system is water cooled and the air is reintroduced into the intake horn. Therefore the recirculated exhaust will not be feeding through the turbo and the intercooler, leaving these components cleaner than they would otherwise be. The sealed crankcase vents to the intake side of the turbo after going through an air/oil separator. Special attention was paid towards minimizing the amount of oil that would be circulating through that system.

The fuel system is a new higher pressure version of the existing common rail system. It now runs at 1800 bar versus 1600 bar for the existing 2006 trucks. This system includes a new rail, larger fuel lines all the way to the injectors, and a new higher pressure CP3 pump.

Front view of the new Cummins 6.7 liter engine.

We tried to find out information on how this all applies to the upcoming regular, non-commercial, 2500 and 3500 trucks and everyone was tight-lipped with information. We were, however, told that the Ram 2500 and 3500 models for early 2007 production will be manufactured with the existing 5.9 liter engine.

Quad Cab configuration.

Regular body configuration.

Since Dodge rarely tools-up components for a single model truck, we feel it is likely that there will be further model introductions. The frame for this truck is all new as is the six-speed Aisin automatic transmission. Since we were told that this transmission would not be used in the regular 2500/3500 series trucks, nor will the frame, speculation is that there will be larger 4500/5500 model trucks released in the future. Since the 6.7 liter engine is compliant with the January 01, 2007 emissions regulations it is almost a “given” that this engine will trickle down to the regular 2500/3500 series trucks as a 2007.5 engine introduction, likely with higher outputs at that time in order to trump the competition.

Service Body truck.

Service Body truck.