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Dodge Was Diesel Before Diesel Was Cool

The diesel truck bandwagon was not a big one in the 1930s. In fact, during the late 1930s, less than a thousand diesel trucks of all types were being sold annually by all manufacturers combined. Among the practical obstacles to on-road diesels were engines downsized enough to fit existing truck chassis, lack of infrastructure (fuel, repair facilities, etc.), initial cost and cold starting capability. Technology was gradually reducing these negatives and substantial fuel savings with diesels was making some operators take a second look. In 1939, gasoline was $0.16 to $0.19 per gallon, while fuel oil was $0.04- $0.10 per gallon. Plus, diesels were about 30 percent more fuel efficient that gas engines.

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Exactly why Dodge decided to design their own diesel engine in the mid 1930s and enter the tiny diesel truck market is unclear. They didn’t have much initial competition but diesel power was definitely ahead of the popularity curve at that point. Still, the early bird does sometimes get the worm and they saw an open market. It’s obvious they began by licensing the Lanova Power Cell system from the Lanova Corporation, based in Germany but with a U.S. corporate arm. If you follow this column and Tractor Talk, you’ll know “Lanova” has come up many times. It was a pivotal element in the progression of four-stroke diesel power. Check out the illustration nearby to understand how it worked and why it was important.

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The last automotive iteration of the Dodge diesel was in 1942. Visually, there was nothing to mark the changes from 1939. The engine weighed a hefty 1,340 pounds but was only about 200 pounds heavier than it’s T124 gasoline brother. The automotive version was complete with a vacuum pump to operate the truck’s vacuum brake booster and windshield wipers. The engine cranked via 24-volts (four 6-volt batteries) but the truck electrical system was 6-volt. As a result, the engine had two generators, one 24-volt unit (the inner one driven by two belts) and one 6-volt (the piggyback, facing backwards), the belt for which also drove the vacuum pump. The diesel trucks used hydraulic clutches.

Period sources indicate Dodge began the development process for the diesel sometime in 1935. A 1939 SAE paper written by a Dodge engineer states they had five fully-developed test engines installed in trucks for operational tests by early 1938. It isn’t exactly clear if the diesel’s architecture was based on an existing gasoline engine or not. It’s clearly very similar to the 331 cubic inch, T43 Dodge HD truck block, a 100 hp flathead six with the same 3.75 x 5 inch bore and stroke. The T43 debuted for 1937 but the diesel was in development at the same time so they could have been concurrent projects.

The T84 diesel powered truck debuted at the December, 1938, NYC Motor Truck Show along with an updated T80 gasser. One of the key features of both engines was an almost identical lower end, featuring a beefy seven main bearing crankshaft with 2.31-inch diameter rods and 3.00-inch mains. Of course all the valve-in-block hardware was eliminated in the diesel but the blocks were still very similar. The diesel head featured the aforementioned Lanova combustion chambers, overhead valves, a 14.75:1 compression ratio, plus individual intake and exhaust ports for each cylinder. The head was well secured with six studs per cylinder and used hardened seat inserts for the Stellite exhaust valves.

…into the early 1950s, NOS Dodge engines, power units and parts turned up advertised in the backs of magazines

When the T84 debuted, it was advertised at 95 horsepower at 2600 rpm and 226 lbs-ft at 1000 rpm. The companion T80 gasser was advertised at 100 horsepower at 2800 and 230 lbs-ft at 800 rpm. For 1940, the T84 diesel morphed into the T106 and the T80 became the T104, with no changes in rated output. For ’41 and ’42, the T106 diesel became the T126 and delivered 100 horsepower at 2600 and 240 lbs-ft at 1200. The gasser (now called the T124) rose to 110 horsepower by virtue of a compression ratio increase. Though torque was the same as the diesel at 240 lbs-ft, it again peaked at a lower 800 rpm.

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The IND-3 version used by the military. It’s not illustrated with any particular attachments, but some of the civilian units have been seen with directly-driven shafts and transverse belt pullies, or with a clutch housing and a keyed output shaft. The military manual rated the engine shown at 61 horsepower at 1800 rpm and 191 lbs-ft at 1200 rpm.

Beyond calibration, the fuel system remained the same on the Dodge diesels through their ’39-42 run. They used an Ex-Cell-O KB swash plate injection pump and single-orifice Bosch injectors that popped at 2,200 psi. The pump and camshaft were driven by gears and the pump could be timed via an access plate on the front cover. The engine was spun over by a 24-volt electrical system and the truck featured a heating coil in the intake manifold for cold starting. Dodge claimed the engine could start in 10 seconds or less at -10F.

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In 1938, Chrysler engineers compared the full-load fuel economy of the T80 gas and T84 diesel on a dynamometer at 2400, 1600 and 800 rpm. The results were telling.  At 2400 rpm, the diesel used 6.6 gallons per hour while the gas engine used 10.7 gph. Even more dramatic, at full-load 800 rpm operation, the gasser stayed at about 10.7 gph while the diesel improved to 4.3 gph.

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The partial cutaway view shows the stout, 7-main lower end. You can see the flathead gasser influence in the low location of the camshaft and the side covers above it. The large unadorned area above the covers is where the flathead’s intake and exhaust valve would have been, as well as the valvegear. The intake heating coil is visible inside the central air inlet. Dodge touted the recirculating cooling system and coolant flow director within the block. Note also the engine has an early closed crankcase system, with the crankcase vented to the intake manifold.

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The ’39-42 Dodge diesel trucks are so rare that we couldn’t find any images to present. The only visual difference from a gas truck was a “Diesel” badge on the leading edge of the hood sides, as shown in this image captured from the 1941 3-ton brochure. Some sources also list these trucks a 4-tons. Shown is a ’41 3-ton WKD tractor hauling a fuel trailer. They came standard with a 5-speed manual (non overdrive) transmission and the standard single speed axle had a 7.4:1 axle ratio (5.8:1 or 6.18:1 ratios optional). The WKDA two-speed axle models had a 6.14:1 ratio in high and 8.35:1 in low. The trucks came as cab and chassis from the factory but dealers could fit a variety of bodies or 5th wheels and a larger variety could be installed aftermarket.

Along the same lines, they road-tested two identical 3-ton Dodge trucks, one diesel one gas, and ran them together 37,000 miles over a variety of roads and terrain with capacity loads. The gasser averaged 3.74 mpg overall while the diesel delivered 5.23 mpg. On 6,000 miles of flat ground testing, the gasser averaged 4.2 mpg and the diesel 6.03. This data was used in a strong push to sell diesel trucks to a skeptical market… but then World War II came along.

From period advertising and truck manuals, we see the diesels offered in the ’39  2-ton TLD/TLDA line and the 3-4-ton TKD/TKDA, which were conventional cab trucks with four wheelbases from 152 to 205 inches. The “A” in model designation indicated a 2-speed rear axle. They were duplicated in the 1940 VLD/VLDA and VKD/VKDA models. They carried over again for 1941 as the Dodge WLD/WLDA and WKD/WKDA models. In ’42, mandatory war production had begun, so the model year was limited and the trucks retained the ‘41 designations. The Dodge 3-4 ton diesel truck line was duplicated under the Canadian Fargo banner from ’39-42 with different model designations and slightly different styling. After consulting  period Branham Automobile Reference Books and Dodge Serial number references, we could not find the T126 diesels offered in any Dodge trucks after 1942.

Chrysler Corporation had industrial and marine engine divisions so the diesel was also adapted for these applications. The company tended to divide them by referring to the truck engines as “Dodge Diesels” and the industrial applications as “Chrysler Diesels” (sometimes as “Chrysler Marine” or “Chrysler Industrial”). We found very little published on the Chrysler diesels until after the trucks were gone. A 1940 SAE paper mentioned that in 1939, Dodge diesels were used to power deep well farm irrigation pumps in Nebraska, pumping 1,300 gpm at 1800 rpm using 3.43 gph. Marine engines were also mentioned as being made available at this time but it’s clear the Dodge trucks were the focus into 1942 and the industrial side ramped up after.

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The power and torque graph for the truck version of the T126. We have seen a chart that superimposes the comparable T124 gasser’s graph over this and they match closely. This is why Dodge didn’t change any of the gearing for the diesel. After testing, it was discovered the trucks were nearly equal in terms of overall performance, with each winning a few points in specific situations. The testers noted diesel’s superior torque rise enabled it to hold a gear a little longer on grades versus the gasser, while the gasser accelerated a bit better.

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Ex-Cell-O is not a household name in fuel injection these days, but it was one of the top systems back in the day. Ex-Cell-O was a big company, best known for building machine tools but in 1927 branched off into fuel injection. They were among the earliest companies to field a relatively simple and cost effective diesel fuel injection system. They also became known for developing injection systems for gasoline aircraft engines. This Ex-Cell-O KB was a swash plate rotary style pump with a built-in transfer pump. The companion single-orifice injectors came from Bosch and popped at 2,200 psi when new and 2,000 psi used. The transfer pump (mounted on the bottom of the housing in this view) put 35-55 psi into the pump. One filter was used ahead of the transfer pump and one between the transfer and the injection pump. Fuel quality was a serious problem in this era and most of what was called “diesel fuel” was actually low grade fuel oil used for heating and steam plants. Low quality and dirty! Plugged injector nozzles were a common problem and one reason why Dodge ran with a single, large-orifice injector that was less prone to plugging. Ex-Cell-O apparently left the diesel injection business in the early 1950s for reasons we could not discover.

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The Lanova Power Cell was called the Twin Cyclone by Dodge. Here’s how it worked: The injector (upper) sprays across the combustion chamber, some directly into a small prechamber called an energy cell. The air in the cell is hotter than the rest of the combustion chamber, so about 40 percent of the fuel ignites in there and the flame front travels back out of the cell into the main chamber, creating turbulence and igniting the remaining 60 percent of the charge. Dodge claimed the initial combustion created 1,100 psi pressure in the cell but when the ignition occurred in the main chamber, it was only 700 psi overall. Combustion occurred slowly and gently, but surely. As a result, the Lanova system eased the stress on engine components during the power stroke so the engine structure could be made lighter duty… and lighter. It had the added benefit of making the engine smoother and quieter, an important part of transitioning the public to diesel. The Lanova diesels also delivered among the highest diesel fuel economy among the other systems out there at the time. It had some inherent power limitations but these did not count for much until later. As higher pressure injection systems evolved and were better able to atomize fuel, the Lanova Power Cell fell to the better-breathing, direct injected combustion engines with greater power density.

When World War II started, much of Chrysler Corporation was mobilized for the war effort. There is a vague historical reference indicating the Chrysler diesels might have been considered in 1941 as a twin-bank tank power-pack. This obviously went nowhere and the more familiar and much more powerful 6046 twin-bank GM 6-71s emerged victorious as the designated diesel tank power-pack. It’s known some T126 diesels were purchased for government service and covered in a tech manual (TM 5-5406). The manual indicates some 600 power units (serial numbers IND-3-2000 to -2600) were purchased, but not how or where they were used. They were different than the civilian power units in some respects.

The power unit was designated IND-3 and generally rated at 60 hp at 1800 rpm but sometimes 80 hp at 2000. Known configurations included bare engines with no driven system, a direct belt drive and a shaft drive with a clutch. The marine versions were designated Type R in some publications and M-12 in the Chrysler Marine catalog, with various ratings up to 82 hp at 2400 rpm. They came complete with all the marine accoutrements; water cooled exhaust manifold, heat exchanger, raw water pump and reduction gears from 1.4 to 9.1:1. Little could be discovered on the extent of marine engine use, but we found Chrysler marine diesels were installed in boats built by Kettenburg Marine in San Diego. A surviving M-12 shows the serial number of 1,858, indicating at least 857 marine units were built. One surviving IND-3 industrial diesel has been found with a serial number in the 3,700 range, and considering the IND-3 serials also started at 1001, we now know at least 2,699 were made.

It appears the bottom fell out for the Chrysler diesels sometime in 1945 or 1946 but we found no information as to why. From then into the early 1950s, NOS Dodge engines, power units and parts turned up advertised in the backs of magazines like The Billboard  (a carnival magazine) at bargain prices. Chrysler must have had a “fire sale” and it appears equipment dealers all over the country bought them and tried to make a few extra bucks on the obsolete NOS engines. So ended the first Dodge diesel.

Today, there are only a handful of ’39-42 Dodge diesel trucks known to survive, plus a few loose engines and industrial units. Production numbers for ’39-42 Dodge diesel trucks of all types is listed as 606 units. We have no reports on how this engine performed, nor it’s record of reliability. On paper, it seems to be one of the better four-stroke diesel engines of it’s era. The engineering department of Chrysler Corporation was at a pinnacle of expertise and forward thinking in this era, but perhaps the Dodge diesel was too good and too soon for a market not yet convinced of the benefits of diesel power.  Still, Chrysler Corporation goes down as being virtually tied with Mack as the first truck manufacturer to design and build it’s own diesel engine.

 The last automotive iteration of the Dodge diesel was in 1942. Visually, there was nothing to mark the changes from 1939. The engine weighed a hefty 1,340 pounds but was only about 200 pounds heavier than it’s T124 gasoline brother. The automotive version was complete with a vacuum pump to operate the truck’s vacuum brake booster and windshield wipers. The engine cranked via 24-volts (four 6-volt batteries) but the truck electrical system was 6-volt. As a result, the engine had two generators, one 24-volt unit (the inner one driven by two belts) and one 6-volt (the piggyback, facing backwards), the belt for which also drove the vacuum pump. The diesel trucks used hydraulic clutches.