International Harvester Nearly Nailed The Diesel Pickup Right Before Its Collapse

Diesel pickups are widely beloved today, but it wasn’t always thus. Once upon a time, the idea of a regular pickup with a diesel engine was a strange and alien idea. The Big Three would eventually start fiddling with the idea in the late 70s, but someone else got there first. That brand was International Harvester, via the Scout. Had a couple of things gone differently, the company could have dominated the space from the get-go. Instead, what follows is one of the great “what if” stories from modern automotive history.

In 1971, International Harvester released the Scout II, an updated take on the original Scout. From launch, it was sold as a two-door SUV, though the term wasn’t in vogue yet. In 1976, the Traveller and Terra were added to the lineup. The latter was a pickup body style, intended to take the place of the now-discontinued International Light Line pickup.

That same year, diesel power would become available for the Scout II. The brand had experimented with diesel engines in its other pickup lines before, but this time, it was a serious option any customer could order. In fact, International Harvester had a diesel pickup ready to go a full two years before Dodge or Chevy could offer the same.

Buy It In

You might think that International Harvester (IH) would have dropped its own diesel engine into the Scout II and called it done. However, that wasn’t the case. Several engines were selected for trials to determine which would be the best fit, including those from other automakers.

As covered by Diesel Power, the exact history is spotty, but reports and surviving test mules indicate that quite a few engines were trialed for the Scout II in the early 1970s. The Peugeot XDP-6.90 was allegedly discounted for poor fitment, while IH’s own D301 was seen as too thirsty, too ancient, and too big to do well, either. The Perkins 6.247 was also tested, but there were concerns around the supply of the then-new design. Allegedly, the Mitsubishi 6DR5 was also trialed and ruled out, though that engine would eventually show up in Dodge’s own abortive diesel truck effort.

In the end, International Harvester landed on the Chrysler-Nissan CN633. With a displacement of 198.5 cubic inches (3.3 liters), it offered similar horsepower to the other engines in the trials. It was selected on the basis that it fit better than its rivals and it was readily available. Good fuel economy and low maintenance requirements were also points in its favor. Despite the name, it was really just a Nissan SD33 that was being built in a partnership with Chrysler that would eventually dissolve. When the partnership ended, the Scout II just switched to Nissan-supplied units.

In 1976, the diesel was made available with the Scout II, including the Terra and Traveller models. An early review by Motor Trend in 1977 states it offered 92 horsepower and 137.5 pound-feet of torque. Reports suggest it was initially available with either a manual or an automatic, though brochures from 1979 suggest it could only be had with a four-speed manual gearbox later on. Indeed, those later documents also quote a lower figure of just 81 horsepower.

It wasn’t a whole lot of power, and progress in a diesel Scout II was slow. Motor Trend’s review posted a zero to 60 mph time of 39.5 seconds, and a quarter mile in 25.1, which was hilariously slow even for the Malaise Era. That’s what you get when 92 horsepower is charged with hauling around a 4110-pound truck. In part, though, that may have been due to the fact that the magazine reviewed the truck with the wide-ratio four-speed manual and the long 3.54:1 rear axle ratio. The close-ratio ‘box with the quicker 4.09:1 rear end would have been much faster, but anecdotally still probably in the 25-second range.

Ultimately, the truck had both strengths and weaknesses. The truck was celebrated for its low-down torque, but was considered poor for on-road duties. “For slugging along rough back country, climbing steep unpaved grades, or pulling stumps, the Terra diesel is just the right truck. On the highway or in traffic, performance is disappointing,” read the review. Indeed, the magazine considered the truck slow enough to put it in a drag race – up against a human runner.

In the first attempt, neither runner nor truck redlighted. The diesel screamed to its limit in 1st gear while the runner gained distance at every stride, but 225 ft down the strip he was finally overtaken. Several runs later, as the runner tired, the overtaking distance was cut down to 190 ft. This started a whole new speculation as to how well a 400-meter sprinter would do under similar conditions, but as the world’s best sprinters in this calss were tied up at the Olympics, the matter was soon dropped.

Fuel economy was decent, though, with the magazine recording 15.6 mpg on its test loop. It noted 10 mpg would be more typical for a contemporary gas truck. At prevailing gas prices, it figured on a saving of up to $475 on gas in 20,000 miles. However, given the $2,265 price tag of the diesel option, the magazine noted it would take around 95,000 miles of driving before you broke even. The magazine also noted that diesel wasn’t readily available outside of major truck stops – which made sense, given that diesel passenger cars weren’t a thing at the time.

Diesel Scouts were built in their thousands. They’re pretty rare, but there are still plenty of examples around.

International Harvester may have beaten Dodge and Chevy to the punch with a diesel pickup for the masses, but it had hit snags just like the big guys would in turn. The truck was slow, the gearing was iffy, and it wasn’t really resonating with consumers. Perhaps the main saving grace of the Scout diesel was that it didn’t suffer the same reliability problems that dogged Chevy’s first attempt.

Worse, as the end of the decade loomed, International Harvester was dealing with all kinds of problems. The company’s finances were in turmoil, workers were on strike, and investors were growing frustrated with management. But the beleaguered company had one more trick up its sleeve.

On The Precipice of Greatness

Late in 1979, with alarm bells going off upstairs, the Scout II was about to get a last hurrah. Where Chevy and Dodge were failing to win hearts with their faltering diesel programs, International Harvester had an ace up its sleeve. For 1980, the breathless SD33 would be swapped out in favor of the Nissan SD33T—the turbo version of the same engine.

Anyone who has driven a turbocharged diesel will tell you the difference is night and day. To that end, the SD33T offered 101 horsepower and 175 pound-feet of torque. Now, an additional 20 hp in a modern 300-horsepower car might not seem like a lot, but it makes a huge difference compared to the 81 horsepower quoted in the 1979 brochure. That’s an increase of 25%!

The additional power meant the engine didn’t have to work so hard, and that netted further benefits to fuel economy. Advertisements quoted EPA figures of 22 mpg, or 24 mpg on the highway. These were truly stellar figures compared to gas trucks of the era, and a cut above rival diesel trucks, too.

Four Wheeler reviewed the new diesel donk in 1980, and noted the significant improvement the turbo brought to the table:

In 1978, we tested the old diesel six and found the highway performance nothing short of embarassing. On a steep grade along State Highway 101 to Northern California, the old diesel dropped speed from 55 like someone had thrown out an anchor. By the time we crested the hill the rig was doing 25 mph, floored in second gear! Even the 18-wheelers were passing us.

Naturally, we had to take the turbocharged diesel over the exact same route just to remain humble. All humble aside, the new IH mill held a steady 55 mph, and just short of the crest we put the pedal to the metal and passed just about every car on the road.

The magazine also noted the engine’s good fuel economy. The truck reportedly returned over 22 mpg on the road, and 18 mpg in off-road use.

What would be truly interesting is to know how the turbodiesel Scout compared directly to its rivals. It had the benefit of forced induction, but it was also rocking a much smaller engine. Dodge had a 4.0-liter Mitsubishi straight-six making 105 horsepower and 169 pound-feet of torque. Chevy’s Oldsmobile diesel engine was a hefty 5.7-liter V8 putting out 105 hp and 205 pound-feet of torque once it was detuned for more reliability. The 3.3-liter Nissan engine in the Scout, even with the turbo, was down on power to both, and only slightly ahead of the Dodge on torque. The turbo probably helped the torque curve and drivability a lot, but on paper, the Nissan engine wasn’t definitively ahead.

Close But No Paradigm Shift

In and of itself, the numbers aren’t enough to say that the Scout nailed the diesel truck outright. But I reckon International Harvester got pretty close. All the ingredients were there: good fuel economy, low down torque, and more top-end power courtesy of boost. A few more years to perfect the formula, and it could have really been something.

In any case, the turbo model was much more popular than the previous diesel Scout. According to Diesel World, International Harvester saw a spike of 1,600 diesel sales in the first year, which then tapered off. However, when the turbo hit in 1980, they sold 5,400 examples. It could have been that the Scout was on the chopping block as International Harvester reorganized amidst corporate turmoil. Or, it could have been because people loved the turbo.

Either way, it showed that International Harvester was on to something good. Scout production ended after 1980 and the diesel went with it, but IH’s story didn’t end there. Ultimately, the company linked up with Ford to produce a line of V8s that kicked off the Blue Oval’s successful journey in the diesel truck world.

Of course, it’s common knowledge today that turbochargers and diesels are a match made in heaven. Dodge would later figure that out with Cummins power in 1989, but International Harvester was almost a full decade ahead. Maybe in another universe, we’d still be driving Scout pickups today with a whole different family of engines under the hood alongside today’s popular diesel trucks. We’ll always wonder.

Image credits: International Harvester