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1989-1993 Dodge D/W 250 & 350 with 5.9L Cummins 12V Diesel engine

If you’re familiar with diesel trucks, you’ve probably heard of the first generation Cummins. In my opinion, it’s by far the most reliable diesel engine ever put into a pickup truck, with the only close competition coming from the 7.3L Powerstroke. Even today, 30 years later after their inception, there are multitudes of 1st Gen 5.9L Cummins trucks on the road. When the 5.9L 12-Valve Cummins engine was introduced to Dodge’s D/W truck lineup, it created a new standard for OEM diesel performance. The 1st Gen 5.9L Cummins had unique specs never before seen on a diesel pickup truck, including a Holset fixed geometry turbocharger and direct fuel injection. These allowed Dodge’s D/W 250 and 350 to give truck owners a best-in-class 400 lb-ft of torque while also improving drivability and throttle response.

Although the 160 horsepower and 400 lb-ft of torque doesn’t seem impressive by today’s standards, they were very impressive for the time. Today, we know the first gen Cummins to be capable of producing high horsepower and torque numbers incredibly easily. High performance numbers can also be achieved cheaply, and the 6BT engine is more than capable of handling extra power without adding too many support modifications. We’ll go into more detail on increasing performance on our first gen 5.9L Performance upgrades post.

1st Gen 5.9L Cummins Reliability

There are a lot of contributing factors to the impressive reliability of the 5.9L Cummins. The engines were built to be robust, because they were initially created for commercial and agricultural applications. They also lacked modern emissions devices and complex electronics, both of which give greater opportunities for failure. Have you ever heard of the acronym, “KISS”? It stands for “keep it simple stupid”. That’s exactly what Cummins and Ram did. By using an inline-6 engine design, they had less problems because they had less parts. These engines also take up less space than a traditional V8, making it so easy to fix and work on these trucks.

Variations of the 5.9L Cummins are often used in race competitions or sled pulling events because of their ability to take a beating. Here are some of the key features that make these engines so durable.

• Gear-Driven Components
• Large Crankshaft & Forged Steel Connecting Rods
• 7 Main Bearings
• 6 Head Bolts per cylinder
• intercooler
• turbocharger

Key Performance Characteristics

The fuel injection and forced air induction systems play a major role in 5.9L Cummins performance. The 12v 5.9L Cummins was the first engine to deploy direct injection as its fuel injection strategy. It was also the first to offer a turbocharger and an intercooler.

5.9L Cummins Fuel Injection System

Unlike Ford or GM’s 8 cylinder diesel pickups during the same time period, the 12v Cummins used direct injection. Direct fuel injection results in greater efficiency by injecting fuel directly into the combustion chamber. There isn’t any pre-combustion event and it led to noticeable power gains over traditional indirect injection engines.

Forced Air Induction System

The 1st Gen Cummins was the first 3/4 ton and 1 ton diesel engine to use a turbocharger to increase performance. It was revolutionary for the time, and had a huge impact on drivability and towing capability. Turbochargers increase the amount of compressed air getting to the engine by using exiting exhaust gases. More condensed air means more power, fuel economy, and better towing performance, especially at higher altitudes.

An intercooler was added in 1991 to further enhance the air induction system. Intercoolers cool the compressed air from the turbocharger, creating denser air that enters the engine. Denser air results in a more efficient combustion process. That means greater fuel economy, lower EGTs, and more power. This feature makes the 91.5-93 model year trucks slightly more desirable than 89-91 trucks.

First Gen Cummins Transmissions

The 5.9L Cummins engine could be paired with either a manual or automatic transmission. The Getrag 5-speed manual transmission is the ideal partner to this Cummins engine. It holds up to extra horsepower the best, and with the addition of a performance clutch, it can help make some big numbers. The early automatic transmissions were clunky, and don’t hold up to the extra power as well. They’re also more expensive to fix and rebuild. The two automatic transmissions available on the 1st Gen Cummins are the A727 Torqueflite 3-Speed Automatic and the 4-speed A518, or 46RH, automatic transmission with overdrive. The 46RH is more desirable between the two automatic transmissions as it will allow for much better fuel economy.

Transmission Options 1989-1993 Dodge Diesel Trucks

Take a look below at the chart to see the available transmissions on 1989-1993 Diesel Ram trucks. I included a ranking system to show which transmission is most desirable. The standard transmission on Cummins diesel trucks is 5-speed Getrag 360 and it is also the most desirable.

1st Gen 12 Valve 5.9L Cummins Specs

First Gen 5.9L Cummins History

Ford and GM already had diesel trucks available with vastly superior torque, towing, and fuel economy compared to Dodge’s gas-guzzling line-up. Sales were low, and Dodge needed an answer. In 1989, Dodge partnered with Cummins, incorporating a 5.9L 12-Valve Cummins engine into the D/W 250 and 350 trucks. The first generation Cummins engine single-handedly saved Dodge’s truck line-up, and gave them the ability to compete with Ford and GM.

This first engine supplied by Cummins is known by a couple of different names including the 6BT Cummins or 12-Valve Cummins. People familiar with the diesel industry refer to Dodge’s 1989-1993 D/W 250 and 350 lineup as the 1st generation Cummins. The engine was originally used in agriculture solutions which turned out to be a great thing for owners. These trucks are built incredibly solid, almost over-built for a 3/4 ton or 1 ton pickup truck.

The partnership between Dodge and Cummins was so successful that it still exists, with a new 6.7L Cummins engine used in Ram’s 5th Generation trucks today.

1st Gen 5.9L 12v Cummins Tow Capacity And Payload

1st Gen 5.9L 12v Cummins towing specs vary depending on cab and model configurations. Max tow capacity for a First Generation 5.9l Cummins is 11,900 lbs. Take a look at your owner’s manual for the exact towing and payload limitations of your vehicle.

First Gen 5.9L Cummins Cab Specs

You’ll find a list of 1st gen 5.9L Cummins cab specs below. These cab specifications are based off of the 1993 model year Ram D/W 250 and 350 trucks. Crew cabs weren’t available on these models. The two cab configurations were regular cabs and club cabs. The Club cab truck is the equivalent of today’s extended cab. They had long and short bed configurations available with both regular cabs and club cabs.

1993 Dodge Ram Truck

Interior Specs

1993 Dodge Ram Truck

Other First Gen Cummins Resources

Learn more 1st Gen 5.9L Cummins specs and information in the resources below. Click on the links to go to that page.

• 1st Generation Cummins Maintenance Guide & Parts List
• Best 1st Gen Cummins Performance Upgrades