<%@LANGUAGE="VBSCRIPT"%> ROCKCRAWLER.com - 2500 Heavy Duty Dodge Ram HEMI

2500 Heavy Duty Dodge Ram HEMI

By Mike Cohn

Discuss This Article Send this article to a friend!

That thing got a Hemi?"Hey! That thing got a HEMI?"



"HEMI®." Just saying the word makes you feel powerful. Try it.


Feels good, doesn't it? Those motorheads in the latest Dodge commercials sure think so, anyway.

With a heritage dating back to the 1930s, the HEMI engine began life as a liquid-cooled aircraft engine. Chrysler's engineers had developed a supercharged and turbocharged upside-down V-16 to battle Rolls-Royce's Merlin engine, used in the Spitfire aircrafts, among others. The name came from the hemispherical design of the the cylinder head.

HEMI ChargerIn 1951, "the dual rocker" 331 c.i.d. motor appeared in Chrysler cars. The theory behind the motor (and any motor) was that the easier an engine breathes, the greater its volumetric efficiency and the more power it produces. The hemispherical combustion chamber design allows large valves to be located across from each other instead of side-by-side, which creates cross flow and free flow between the intake and exhaust ports. What that means is a more complete burning of the air/fuel mixture coming from a central spark plug, located close-by. The design also minimized heat loss, which in turn, means more energy. The name "hemispherical" comes from the fact that the smallest amount of space that can contain a given volume is a sphere. A hemispherical combustion minimized the surface area, thus minimized heat loss.

Though considered to be a great engine, the 180 hp FirePower V-8 would last in production for only eight years. At the end of its run, it had grown to be a 392 and put out 390 hp. A racing version was tested in 1952, but was banned for use in the Indy 50 because its speed would outrun the rest of the field.

The HEMI made other showings, such as the 276 c.i.d. used in DeSotos, and later, a 241 c.i.d. "Red Ram" used by Dodge from 1953 through 1957. This model finished its production life as a 325 c.i.d.

But the one HEMI that everyone thinks of first, was of course, the 426 Race HEMI. Former models were dropped from production because of their complex (read, expensive) design compared to their competition. Instead, Dodge was making simpler engines bigger, despite being less efficient than their predecessors. But by the early 60's, Chrysler was losing too many races at the track. Their NASCAR dominance of yesterday had waned and they were eager to regain the top position. What would get them there was the HEMI. The 426 c.i.d. was built. The race version featured high-flow heads, tubular headers, a potent 12.5:1 compression ratio, and a single, four-barrel carburetor. Plymouth and Dodge once again became top finishers, proving that what won on Sunday, sold on Monday.

5.7L HEMIMeet Today's HEMI
Fast forwarding to 2003 (model year, anyway), Dodge has re-introduced the HEMI motor. According to the folks at Dodge, the new 5.7L HEMI Magnum V-8 is less expensive to build than an overhead cam engine, but produces comparable power. Learning from the technological advances over the last few decades, the new HEMI uses aluminum cylinder heads to reduce weight, fuel injection and electronic throttle control, and two spark plugs per cylinder and coil-over-plug ignition to improve combustion efficiency even further. It also uses a high-mounted camshaft to shorten the pushrods and stiffened rocker arms.

So why the long history lesson on the HEMI? Well, in case you've been living under a rock lately, Dodge's new 2500 and 3500 Heavy Duty pickups now feature the HEMI as the standard engine. Not only that, but the HEMI is also set to be available in 2003.5 Ram1500 pickups, the 2004 Dodge Durango and possibly even other models, including cars, in the DaimlerChrysler lineup.

Not nearly as large as the big blocks of old, the new HEMI is a 345 c.i.d. engine. The eight cylinders (16 valves) run a 9.6:1 compression ratio and crank out 345 hp (5400 rpm) and 375 lb.-ft of torque (4200rpm). This represents a 41% power gain and 12% greater torque than the 5.9L Magnum V-8 it replaces. See the chart below to see how this compares to the other gas-burning motors on the market today.

  Dodge 5.7L HEMI V8 Ford 5.4L V-8 GMC 6.0L V-8 GMC 8.1L V-8 Dodge 8.0L V-10 Ford 6.8L V-10
HP 345 @ 5400 rpm 260 @ 4500 rpm 300 @ 4400 rpm 340 @ 4200 rpm 305 @4000 rpm 310 @ 4250 rpm
Torque 375 @ 4200 rpm 250 @ 2500 rpm 360 @ 4000 rpm 455 @ 3200 rpm 440 @ 2800 rpm 425 @ 3250 rpm
Displacement 345 cu. in. 330 cu. in. 364 cu. in. 496 cu. in. 488 cu. in. 415 cu. in.

Studying the chart, each manufacturer's engines horsepower and torque peak at different rpm ranges, so without actually driving each one in a comparable truck, it's difficult to say which would be the "best" motor. If we simply look at the peak values alone, you can see the HEMI is quite the leader in the V-8 range in horsepower and second only to the big block GMC engine. The V-10s, of course, are the torque monsters and beat all, but the HEMI is near the top of the class once again in the V-8s. Where the HEMI is the big winnerl is in the all-around numbers, and being a smaller motor than the V-10s means less of that recommended 89 octane will be purchased each time you visit the gas pump. Where the HEMI does get outclassed is in the towing realm, where the diesel motors rule the landscape with their massive 500+ torque values. But we're talking about gas engines here, aren't we?

The 2003 Dodge Ram Heavy Duty Pickups    (click photos for larger views)
So all this brings us to the reason we're here today - the Dodge Ram 2500HD. In 2002, Dodge began the full-line revamp of the Ram truck line. For 2003, the Heavy Duty line (2500 and 3500 series) get their make-overs. The ladder-type frames are completely new and unique, though similar to the 1500's design. Using hydroformed "box" sections that are far stiffer than previous designs, the frames are now stronger, contributing to better steering and handling precision.

While the 2WD versions use a new rack and pinion steering design, the 4WD versions use a redesigned recirculating ball steering setup. The result is much better steering feel, especially when coupled with the new 17 x 8 inch wheels. The 4WD Rams have a 13.4:1 overall steering ratio and 2.75 turn lock-to-lock. Though not nearly as tight a circle (what is?) as GMC's Quadrasteer trucks, the new Rams are much more maneuverable than previous models - especially when in tight spots.

2003 Dodge Ram Heavy Duty HEMI
2003 Dodge Ram Heavy Duty HEMI

Inside the new frame resides one of four available transmissions, those being:

  • NV4500/NV4500HD Manual, 5-Speed Overdrive (standard. with 5.7L and 8.0L V-8 and 5.9L diesel)
  • NV5600 Manual, 6-Speed Overdrive (standard in 5.9L High Output diesel)
  • 5-45RFE Automatic 5-Speed (optional with 5.7L HEMI)
  • 47RE Automatic 4-Speed Overdrive (optional with 8.0L V-10 and standard output Cummins diesel)
Behind the tranny you have your choice of two new transfer cases - either the NV271 or the NV273. The manual shift NV271 is standard on the ST and SLT models, while the electronic shift NV273 is optional with the SLT trim and standard in Laramies. Low-range on both cases is 2.72:1.

Carrying the weight of a full-size pickup is a daunting task and the new Heavy Duty Rams feature a new suspension system in the 4WD versions. The front suspension is a modified version of the five-link, coil-spring suspension used on previous HD Rams with a new front beam axle. Clearance below the axle is 8.7 inches.

2003 Dodge Ram Heavy Duty HEMI
2003 Dodge Ram Heavy Duty HEMI

The rear suspension is common to both 2WD and 4WD models and uses longitudinal leaf springs, lengthened three inches from the 2002 versions to improve ride quality. The 2500's two-stage springs have three leaves for normal loads and an additional leaf for heavy hauling. The rear box section was also widened to create a wider rear spring span, which also helps combat lean during cornering. These changes actually eliminated the need for a rear stabilizer bar.

All-new axles also adorn the new Rams. The 2500 series' axles use a 10.5 inch ring gear (11.5 inch on the 3500) in the rear and a 9.26 inch in the front. These big-boy axles help the Rams get a best-in-class towing rating in the 3500 diesel models (12,000 pounds). Upgrading the standard 3.73:1 axle ratio to 4.10:1 nets an additional 2,000 pounds of towing capacity. 13.9" disc brakes with ABS are at all four corners.

On to the Test Truck --->>>




Help spread the ROCKCRAWLER world!           Share on Facebook

©1997-2015 ROCKCRAWLER 4x4 and Off-Road Magazine. All Rights Reserved.

RockCrawler.com   -   IH8MUD.com