1989 - 1993 Dodge Ram (12v Cummins)
1st gen Dodge Rams seem to have made a comeback in popularity. From 89 to 93, the Cummins made 160 horsepower and 400 lb-ft of torque. These figures can easily be improved, as the 12v Cummins has an unlimited supply of aftermarket support. The VE44 injection pumps are less desirable than the later P1700 pumps with regard to performance potential, but they get the job done. "Killer Dowel Pin" (KDP) problems affected this model year, which creates potential for a catastrophic failure. KDP repair kits can be purchased in the $50-$75 range; invest in one. The Getrag G360 manual transmission is favored to the automatic and much more reliable.
1994 - 1998 1/2 Dodge Ram (12v Cummins)
The 12v Cummins continued its legacy through midyear 1998. For 94, which kicked off the 2nd Generation Cummins powered Ram, a P1700 injection pump replaced the VE44 rotatory pump. For the 94 to 98 12v Cummins, injection pump modifications alone can yield triple digit improvements. The 94 & 95 model years offered the 47RH automatic while 96 to 98 model years used the 47RE. The NV4500 5 speed manual was offered from 94 to 98 and is favorable over the automatic. The 47RE is known to be problematic; it doesn't seem that it was originally designed to handle the big, low rpm torque that the Cummins makes. However, they can be rebuilt to be very reliable and even beefed up to support massive torque. When it comes time for a rebuild, look into upgraded components.
The NV4500 remains our recommendation, both for preference and the reputation the smooth shifting gearbox has earned. Manual transmission engines also had between 15 and 35 more horsepower during these model years since the automatic wasn't rated to handle the higher output. These model years are also affected by the KDP (killer dowel pin), so plan on investing in a repair kit if the previous owner has not. Some 98 model year 12 valves had #53 block castings, though they are rare and there have been no reports of cracking issues like there have been on 24v motors.
1998 1/2 - 2002 Dodge Ram (24v Cummins)
Halfway through the 98 model year, the 5.9L Cummins was redesigned as a 24 valve engine. Horsepower and torque did not increase over the 12 valve until 2001, when a high output version was introduced. The H.O. Cummins was good for an extra 10 horsepower and 45 lb-ft. From 1998.5 to 2000 manual transmission equipped trucks produced an additional 20 hp and 40 lb-ft over automatic equipped trucks. The NV4500 manual and 47RE automatic transmissions were offered, the manual being favorable. The NV5600 replaced the NV4500 in H.O. models. #53 block castings, which have thin water jackets, are a big concern for these model years. If you're looking for a truck that you plan to play with, you may want to avoid the 53 block casting. If you plan on keeping the engine stock, this should be less of a concern. The blocks don't catastrophically destruct, but they do tend to crack and leak at the water jacket walls. 2002 was the last year of the 2nd gen Dodge Ram, whose body style still had the small grille.
2003 - 2007 1/2 Dodge Ram (24v Cummins)
The 2003 model year kicked off the 3rd generation Dodge Ram. The body underwent significant changes, most notable of which was the introduction of a large grille and smooth body lines. The VP44 mechanical injection pump was replaced by a high pressure common rail system, making these model years extremely popular. A 555 lb-ft high output version of the Cummins was available for 2003, which became the standard torque rating for 2004. The 2004 H.O. version offered 600 lb-ft, compared to the standard 555 lb-ft and the California model's 460 lb-ft (the H.O. was not available to CA residents for emissions reasons).
The H.O. was discontinued when output for the 24v reached its peak for 2005 through 2007 model years at 325 hp and 610 lb-ft. For this reason, the 05 to 07 are prized gems and hold their value relatively well. The NV4500 was the standard manual transmission until 2005, while the 48RE was the standard automatic transmission from 03 to 07. The NV5600 was used on high output models, which were not available with an automatic. For 2006 and 2007, the G56 6 speed manual replaced the NV4500. The 48RE, though stronger than the 47RE used previously, is considered the lesser transmission. If you plan on performing any modifications to your engine, plan on beefing up the automatic. It's generally reliable at stock power levels, though its longevity is questionable.
2007 1/2 - 2017 Ram (6.7L Cummins)
Cummins launched the 6.7L mid year in 2007. The introductory ratings were 350 horsepower and 650 lb-ft with an automatic transmission and a derated 610 lb-ft when coupled with the manual transmission. 2007 was the first time that a manual transmission equipped truck was derated, as historically the automatic equipped Rams were derated. "Dodge Ram" became "Ram Trucks", or just "Ram" in 2010. The 6.7L Cummins uses a diesel particulate filter system, which significantly reduces fuel economy and reliability. Early engines often suffered from DPF clogging. The DPF can be removed via aftermarket equipment, but this technically eliminates the trucks legal status on the street.
The 68RFE 6 speed automatic was standard for these model years, which is leaps ahead of the 48RE in reliability, performance, and longevity. The G56 manual was available, but are rare due to the derated output. In February 2011, the Cummins torque output was increased to 800 lb-ft, while horsepower remained the same. This output was only made available for automatic equipped trucks. The body style was also altered for 2007, as sharper lines and a more refined shape were introduced. In 2013, three variants of the Cummins were introduced. When equipped with the G56 manual, engines are rated at 350 hp and 660 lb-ft. Backed by the 68RFE automatic transmission, output was bumped to 370 hp and 800 lb-ft. A high output 385 hp, 850 lb-ft version was also introduced, mated to a medium duty Aisin 6 speed automatic transmission. For 2015, the H.O. engine saw torque increased from 850 to 865 lb-ft. In 2016, torque for the H.O model was increased once again to 900 lb-ft. The H.O. platform remains only available for 3500 model pickups.