Retiring a semi-truck doesn’t always mean retiring its engine. Older diesel engines can remain valuable long after the trucks they powered have been taken out of service, particularly when replacement parts are available and the major components are still in good condition. Some are rebuilt for continued use, while others end up in equipment that was never intended to operate on a highway.
One of the more unusual examples involves a retired International semi-truck that was converted into a working farm tractor. The project shows how an older truck’s engine and drivetrain can remain useful when the original vehicle is no longer needed for hauling freight.
From Semi-Truck to Farm Tractor
Gerald Oetken and his son Glen of Kansas converted a 1978 International 4300 into a farm tractor, keeping its Cummins engine and Fuller transmission rather than replacing the entire powertrain.
The conversion required extensive work, including modifications to the frame, drivetrain, and rear axle. The engine was rebuilt, and a different governor was installed to help maintain a consistent operating speed during fieldwork. Once completed, the tractor was capable of pulling a 32-foot disk and a 38-foot fallow plow, according to FARM SHOW Magazine.
The International wasn’t simply a truck with different tires. Its owners had to make the equipment suitable for agricultural work, where traction, operating speed, and the demands placed on the drivetrain differ from highway use. By retaining much of the original powertrain, they were able to build a working tractor around machinery they already had.
Why Some Engines Outlast Their Trucks
A semi-truck may be retired for reasons that have little to do with the engine itself. Chassis wear, repair costs, and changes in fleet requirements can make continued operation impractical even when the powerplant remains in serviceable condition.
Older diesel engines can also benefit from an established supply of replacement parts. The Cummins 855 used in the International conversion belongs to an engine family with a long history in heavy-duty applications, making rebuilding a realistic option when the engine’s condition supports it.
Before an engine can return to service, its major components must be evaluated for wear and damage. Rebuilding may involve restoring usable parts and replacing others, but severe internal damage can make the cost difficult to justify. In those cases, the engine may be worth more as a source of components for other repairs.
That distinction matters because an old truck engine doesn’t have to remain intact to be useful. Parts recovered from one engine can help keep another running, particularly when compatible replacement components are still in demand.
Putting Highway Engines to Work Elsewhere
Agricultural machinery isn’t the only equipment that uses heavy-duty diesel power. Engines from manufacturers familiar throughout trucking have also been used in construction equipment, industrial machinery, irrigation systems and generators.
However, an engine found in those applications wasn’t necessarily removed from a semi-truck. Manufacturers have produced different versions of their engines for highway and industrial work, often with changes to controls, cooling systems, and operating characteristics.
Moving an actual truck engine into another machine takes planning. Equipment used for stationary power may need to maintain a steady engine speed for long periods, while highway engines are designed to respond to changing loads and operating conditions. The governor modification made during the International tractor conversion is one example of how those differences can be addressed.
The engine also has to fit the equipment’s power requirements and supporting systems. A mechanically sound diesel isn’t automatically suitable for a generator or pump, particularly when installation costs and applicable emissions requirements are considered.
For that reason, custom conversions tend to depend on the equipment available, the work involved, and the mechanical knowledge needed to make everything operate together.
The Value of an Engine That No Longer Runs
Not every retired engine is a candidate for rebuilding or conversion. Some have accumulated too much wear, while others need repairs that cost more than a suitable replacement.
Even then, usable components can be recovered before the engine is scrapped. Blocks, crankshafts, and other parts may be inspected for possible reuse, depending on their condition and the demand for that particular engine model.
When the remaining components cannot be restored, their metal can be recycled. An engine that will never run again may therefore still have value through its parts and materials.
The Kansas farm tractor is an unusual example of what can happen when a retired truck’s machinery is worth keeping together. Most older engines won’t end up in such a distinctive project, but rebuilding and parts recovery offer other ways to extend the usefulness of equipment after its highway service has ended.
Frequently Asked Questions
Can a semi-truck engine be installed in a farm tractor?
Yes, although the conversion may require changes to the drivetrain, engine controls, mounting arrangement and other systems. The International 4300 converted by Gerald and Glen Oetken is a documented example of a highway truck adapted for agricultural use.
Are Cummins engines used in equipment other than semi-trucks?
Yes. Cummins has manufactured engines for highway and industrial applications, including agricultural and stationary equipment. Engines within the same family may have different configurations depending on their intended use.
Can an older truck engine power a generator?
It may be possible, but the engine must be compatible with the generator’s power and operating requirements. Cooling, speed control, installation costs, and applicable emissions rules can determine whether a conversion is practical.
What happens to a diesel engine that cannot be rebuilt?
Usable components may be recovered for other engines, while damaged or unwanted materials can be recycled. The value of an older engine depends largely on its condition and demand for its parts.
The TDUSA editorial team creates practical, driver-focused content covering trucking news, industry updates, safety, regulations, and career information for professional truck drivers across the United States. Each article is built to reflect real-world experience, industry developments, and information drivers can use on and off the road.
Last Updated: October 20, 2026
