Navistar relies on Cummins for big-bore and medium-duty diesels while putting its resources into a 13-liter-class diesel, along with a proprietary automated manual transmission. Developed in collaboration with European partners, the two components seem to be real accomplishments.
I say that after a recent drive of an S13 integrated powertrain, in mid-summer at the Navistar Proving Grounds in northern Indiana. An S13 diesel and T14 AMT were in a long-nose HX (for Heavy eXtreme) tractor that was as much a highway cruiser as a vocational workhorse. It was hitched to a loaded steel flatbed, and I drove the rig on the facility’s 3-mile asphalt oval and over a gravel trail and several concrete shaker courses.
The long track represents highway travel, where the HX’s ride was comfortable. And the off-road paths test a truck’s toughness, which the HX evidently has a lot of. Over the rough surfaces, the cab and chassis seemed especially stout and there was little or no creaking, groaning, or banging. Nor did much vibration penetrate the air-ride suspensions on rear axles, cab, and seats.
The HX had the strongest 515-horsepower version of Navistar’s S13 diesel, running through a 14-speed T14, which will be standard in most International heavy-duty trucks and tractors using the S13. The new engine will eventually replace the current A26.