For decades, the diesel engines in Ford's heavy-duty trucks were not built by Ford at all. They came from International Harvester, later Navistar. This partnership produced some of the most famous diesels ever put in a pickup, and also some of the most controversial, before it ended in dispute and pushed Ford to build its own engine. Here is the story of one of the auto industry's most consequential supplier relationships.
How the partnership began
Ford turned to International Harvester for diesel power in the early 1980s, starting with the indirect-injection IDI engines. International had deep diesel expertise from its commercial truck and equipment business, and the arrangement let Ford offer a capable diesel option without developing one from scratch. It was a practical fit that would last far longer than anyone might have predicted.
The Power Stroke years
The partnership reached its peak with the Power Stroke name. The legendary 7.3L, the more complex 6.0L, and the compound-turbo 6.4L were all built by Navistar. These engines defined Ford's diesel identity for a generation and sold in enormous numbers. The 7.3L in particular became a benchmark for durability that enhanced both companies' reputations.
Strain and separation
The relationship grew strained during the 6.0L and 6.4L era, as reliability problems and tightening emissions demands created friction. Disputes between the two companies became public and contentious. Ford ultimately decided to design and build its own diesel, and the 6.4L became the last Power Stroke made by Navistar. The long partnership came to an end.
Ford goes it alone
With the 6.7L Power Stroke around 2011, Ford brought diesel development fully in-house for the first time. The move gave Ford complete control over engineering, emissions strategy, and the integration between engine and transmission. The end of the Navistar partnership marked a new chapter, but the engines that partnership produced remain a huge part of Ford diesel history.
The legacy the partnership left behind
Even though it ended in dispute, the Ford and Navistar partnership left a legacy that still shapes the diesel world. The 7.3L Power Stroke, in particular, set a durability standard that owners and enthusiasts still measure other engines against, and the sheer volume of trucks the partnership produced means parts, knowledge, and community support remain strong decades later. The engines built during those years, from the IDI diesels to the 6.4L, form the backbone of the used diesel market and a huge share of diesel history.
The split also proved consequential for the industry. Ford's decision to bring diesel development in-house with the 6.7L gave it full control over engineering, emissions strategy, and the integration between engine and transmission, and the results speak for themselves in the modern 6.7L's success. In hindsight, the strains of the 6.0L and 6.4L era were the catalyst for a stronger, more self-reliant Ford diesel program. The partnership that built the Power Stroke name ultimately ended by pushing Ford to stand on its own, and both the engines it produced and the change it triggered remain central to the story.
Frequently asked questions
Which Ford diesels were built by Navistar?
The IDI diesels of the 1980s and early 1990s, plus the 7.3L, 6.0L, and 6.4L Power Stroke engines, were all built by International (Navistar). The 6.4L was the last one.
Why did Ford and Navistar split?
The relationship grew strained during the 6.0L and 6.4L era over reliability issues and emissions demands, leading to public disputes. Ford chose to design and build its own diesel going forward.
When did Ford start building its own diesels?
Ford brought diesel production in-house with the 6.7L Power Stroke around 2011, its first diesel engineered and manufactured by Ford itself rather than sourced from Navistar.
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