Gearhead News

March 31, 2021
Swapping a John Deere Diesel Tractor Engine Into a 1969 GMC Truck Is Ridiculously Tough

Like every other car nut who spends too much time online, I get bored with engine swaps. Not because they’re too easy like I’m some sort of master mechanic—I assure you, I’m not—but because they flood my Facebook feed and all seem virtually the same. Once in a blue moon, though, something breaks the monotony and my jadedness fades; it’s nice to be astonished like the old days.

Anyone who can swap a John Deere tractor engine into a classic GMC truck, and do it well, certainly stands out. The shop crew from Kern Machinery’s Bakersfield location—mainly service manager Mark Campanella—was able to pull off the unlikely switcharoo while making it look like a factory job.

BTUFF via YouTube

Let’s start by saying this isn’t a leaky, 40-year-old engine. It’s an electronically injected John Deere crate unit that makes somewhere around 170 horsepower stock. That output is produced by four cylinders that get force-fed with boost by a variable geometry turbo and, in this application, it’s sent through a six-speed Allison automatic that was specially assembled for this truck. More details on that later.

Campanella built this truck for Clayton Camp, president of Kern Machinery whose parents got into John Deere sales and service in 1969. That’s why they picked this GMC three-quarter-ton from the same year to pay homage. It originally had a 350 small-block V8 and a four-speed, though it’s since shed its old running gear for a much more modern powertrain. It may be a tractor engine but it has common-rail injection, an exhaust gas recirculation system, and electronic controls throughout. Actually, the 4045HF485 is the most powerful four-cylinder that Deere makes.

Even with it having half the cylinders of the GMC’s original lump, it’s still plenty big. Its displacement measures 4.5 liters and from end to end, it’s nearly seven inches longer than a 350. On top of that, it weighs 1,082 pounds dry and that’s before you factor in the custom bracketry and mounts.

A ton of fabrication was required to make this even feasible, and there’s the slightest bit of clearance between moving parts that makes it obvious. They fitted the largest air-to-air intercooler they could up front, all while packaging the radiator ever-closely to the engine it helps keep cool. 

Circling back to the transmission, Campanella describes it as an Allison 1000 shell with “2000 internals.” In layman’s terms, it’s a six-speed automatic stuffed into a case that typically houses a five-speed unit. There’s a push-button gearshift in the cab, right next to the cruise control switch and digital info screen that displays all types of engine and transmission data.

BTUFF via YouTube

BTUFF via YouTube

The rear axle is equipped with 4.10 gears, and power is split between it and the front by way of a specially built NP203 divorced transfer case. It apparently has enough torque to snap the stock Dana 60s, so they had to go another route there; from the factory, the four-cylinder makes 476 pound-feet of twist.

A quick start of the engine reveals a quiet click-clack that sounds like, you guessed it, a modern John Deere tractor. Camp says you can hold a conversation in the cab without yelling, and it turns much lower RPM than, say, a modern Duramax or 6.7-liter Cummins diesel. According to the manufacturer, it makes peak torque at 1,500 rpm while peak horsepower comes on at 2,400; compare that to a new 6.6-liter Duramax’s numbers of 1,600 and 2,800 rpm, respectively.

You won’t find another truck like it, and you might not even see this one on the road very often. It’s hard to imagine California’s strict tailpipe regulations are fit for highway use of a tractor engine, even with its emissions systems still intact. That’s neither here nor there, though, since this is something anyone should appreciate.

Got a question for the author, or a tip about your own tractor-powered truck? Contact them directly: caleb@thedrive.com