NAPCO Factory 4×4

We should thank NAPCO for factory 4×4.

Dodge was the first company to offer a factory 4×4 option to the consumer market with the sale of the consumer market Dodge Power Wagon – a design that was made for WW2 and proven on the fields of war. While the Power Wagon has a legacy stretching back more than 70 years, its the NAPCO conversion parts that were supplied to General Motors in the early 50s that we really have to thank for the popularization of factory 4×4.

Rarity and Ingenuity: The Early 1955 Chevrolet ½ Ton NAPCO 4×4

So, what sets the early 1955 Chevrolet ½ ton 4×4 with a NAPCO conversion apart from the crowd? For starters, finding one today is like stumbling across the yeti—especially a short wheelbase model that’s survived decades of off-road work and neglect. These pickups weren’t the daily driver of their time. With prices soaring more than 70% above standard models, only those who truly needed off-road capability—think utility companies or rugged tradesmen—bothered to pony up for the privilege.

That means most of these trucks saw hard labor, rarely a sudsy wash, and, after years of service, a one-way ticket to the salvage yard rather than a cozy garage. When you see one restored, looking as fresh as the day it rolled out, you’re looking at a true survivor.

What makes the 1955 model particularly unique?

• First of Its Kind: 1955 was the inaugural year Chevrolet offered a short wheelbase, open driveshaft setup—a crucial feature allowing a half-ton Chevy to even accept four-wheel drive. Before this, such upgrades were reserved for their burly three-quarter-ton siblings.
• Aftermarket Magic: Four-wheel drive was not a factory option until 1957. Enter NAPCO’s ingenious bolt-on kit, shipped in hefty wooden crates from Minneapolis, letting owners and dealers transform ordinary pickups into off-road legends.
• Local Legend: Many were put immediately to work for organizations like the Tahoe City Utility District, where their low mileage reflects dedicated but limited service within a tight radius.
• Engineering Solutions: Owing to unique chassis quirks, NAPCO sometimes modified existing three-quarter-ton axles to fit the new half-ton design. To avoid mismatched bolt patterns between front and rear wheels—an absolute no-go for anyone venturing off the pavement—NAPCO devised clever steel adapters, ensuring eight-lug uniformity all around.

Restored examples, like the one rescued and brought back to life after 30 years of patient waiting, retain original touches: six-volt electrics, an inline 235 six-cylinder engine, and rare factory accessories—right down to the quirky heater and AM radio functional enough to warm you up and keep you in tune while scaling a snowdrift.

In short, the few surviving early 1955 NAPCO 4×4 Chevrolets are rare because of their limited production, unique technical patchwork, demanding lifecycle, and the sheer commitment required to bring one back from the brink. For four-wheel-drive aficionados, it doesn’t get much more special than this.

Northwestern Auto Parts Company started in 1918 in Minneapolis Minnesota. During WW2 NAPCO helped the war effort by producing mechanical components as a supplier to the Big Three. During 1942 NAPCO began building Four Wheel Drive assemblies to be fitted to Ford, GM, Chevy and Studebaker vehicles that were being shipped to Europe and the Pacific. From 1942 to 1956, Chevy and GM trucks could be ordered by the government and civilians with a NAPCO Power-Pak kit that could be installed later, for $995.

Lesser-Known NAPCO Nuggets: The Curious Case of the 1955 ½ Ton Chevy

If you’ve ever wondered just how far NAPCO’s creativity reached in those formative years, the mid-1950s offer up some fascinating Easter eggs—especially in the world of Chevrolet ½ ton trucks.

When Chevy rolled out the last of the Advance Design pickups in early 1955, it also marked the first time their ½ tons ran an open driveshaft, making them eligible for a NAPCO 4×4 system. Prior conversions had always required the beefier ¾ ton or larger frames. But as you might imagine, this meant the NAPCO crew had to get inventive since the front differential housing wasn’t centered like the rear—and Chevy didn’t offer axles to match.

Here’s where NAPCO shines:

• For a short window—roughly five months—NAPCO updated their ¾ ton front axles just enough to fit the new ½ ton configuration.
• The altered axles paired up with the ½ ton’s 3.90 ratio differential (to perfectly sync with the rear end), but used ¾ ton axles on the front.
• The result? The front wheels came standard with eight lugs—borrowed from the larger trucks—instead of the typical six you’d expect on a ½ ton. Quite the sight if you’re a detail spotter.

But NAPCO didn’t stop there. They realized that selling a truck with two different wheel bolt patterns was a non-starter for buyers (and an unnecessary headache for anyone stashing a spare tire in the bed). Their solution was pure American ingenuity: steel adapters bolted onto the ½ ton’s rear wheels allowed for eight-lug wheels at all four corners—using elongated studs and press-fit bolts—so your spare fit everywhere and your truck wouldn’t raise eyebrows with mismatched rims.

It was a brief but ingenious chapter, tidying up one of the more peculiar quirks in early 4×4 conversion history, and proof that necessity really is the mother of invention.

Adapting Heavy-Duty Axles for the Half-Ton

In the early months of 1955, Chevy and GMC introduced their updated half-ton pickups, known as the last of the Advance Design trucks. For NAPCO, this presented a unique challenge—and an opportunity for clever engineering. The new half-ton models now featured an “open drive” shaft system, which meant, for the first time, these trucks could potentially receive a NAPCO four-wheel-drive conversion. But there was a hitch: the front axle setup on the half-ton was unlike its bigger siblings.

Instead of waiting for GM to supply compatible components, NAPCO took matters into their own hands. They modified their existing ¾ ton axle assemblies just enough to fit the new half-ton’s front differential carrier. This allowed them to maintain the crucial 3.90 gear ratio, ensuring proper drivetrain function, but required some creativity with the wheel hubs.

Perhaps the most surprising adaptation came with the wheels themselves. The front axle conversion required using ¾ ton eight-bolt wheels on the half-ton, while the standard half-ton rear still sported the smaller six-bolt pattern. NAPCO’s solution? They crafted steel adapters for the rear wheels. These adapters attached using lengthened six-bolt studs and were fitted with eight new studs, allowing matching eight-bolt wheels front and rear, and ultimately, a single compatible spare. It was a clever demonstration of resourcefulness, making seamless four-wheel-drive functionality possible without sacrificing reliability or field-service practicality.

The 1955 Milestone: Four-Wheel Drive Meets the Short Wheelbase

So, what made 1955 such a turning point for short wheelbase trucks and four-wheel drive? For the first time, Chevrolet introduced a ½ ton truck with an open driveshaft and a short wheelbase—two ingredients that had previously kept light-duty trucks stuck in two-wheel drive land.

Before this, four-wheel drive kits from NAPCO were mostly the domain of beefier ¾ ton and larger trucks. But with the 1955 redesign, suddenly that robust NAPCO Power-Pak was a practical bolt-on for lighter, more versatile pickups. This meant adventurous folks could finally get the best of both worlds: a nimble ½ ton truck with real four-wheel drive capability.

Of course, fitting 4WD into these newly minted ½ tons was not exactly plug-and-play. Due to quirks in axle alignment—unlike the rear, the front differential in these trucks wasn’t perfectly centered—NAPCO had to engineer custom-length axles and housings for the conversion. The result? A new era where even the little guys in the GM lineup could venture confidently off-road.

How Rare Are Surviving Early NAPCO ½ Ton 4×4 Pickups?

Finding an original 1955 Chevrolet ½ ton 4×4 fitted with a NAPCO Power-Pak today is about as likely as spotting a unicorn in your neighbor’s driveway. These trucks were never produced in large numbers to begin with, and decades of hard work, off-road adventures, and rust have steadily thinned the herd.

Surviving examples are cherished by collectors and truck enthusiasts alike, mainly because so few are known to exist. If you come across one in the wild—still sporting its factory NAPCO hardware—you’re looking at a genuine piece of four-wheel-drive history.

In a matter of 3-4 hours and 4 holes drilled in the existing chassis, a 2WD truck could be converted into a 4WD Mountain Goat with a shift on the fly rubber mounted transfer case with low range.

Ingenious Engineering Made Simple

Part of what made the NAPCO Power-Pak so accessible was its clever design. For example, the rear spring bolt hanger in the 1955 NAPCO conversion was engineered to hang down from the frame rail a full 8 inches—substantially longer than what you’d find on a ½ ton model. This thoughtful detail made the installation process smoother, as NAPCO designed these hangers to fit right into the same holes already present in the frame rail from the truck’s original two-wheel-drive setup. Even the original 1 ¾” wide rear spring was retained, seamlessly integrating with the conversion kit.

This meant that whether you were a rancher, a contractor, or just someone craving more capability, you could transform your Chevy or GMC into a true four-wheel drive workhorse in an afternoon, without reinventing the wheel—or the frame.

Tackling Wheel Bolt Pattern Challenges

One of the quirkiest and most ingenious aspects of those early NAPCO conversions lies in the matter of wheel bolt patterns—a detail that owners and mechanics soon discovered was anything but straightforward.

When Chevy’s Advance Design trucks got an open driveshaft in early 1955, NAPCO could finally outfit the lighter ½-tons with their four-wheel drive system. Until then, all conversions had been on ¾-ton and up. But the axles were anything but a plug-and-play affair. The front differential wasn’t perfectly centered and, to complicate matters, the ½-ton trucks used wheels with six lug bolts, while the heavy-duty NAPCO-supplied front axles had eight.

NAPCO’s fix was as creative as it was practical. With a short window to get these new ½-tons rolling off the lot, NAPCO adapted its existing ¾-ton front axles to fit. That meant eight lug bolts on the front wheels—unusual for a ½-ton that would normally have six.

But you can’t have two different bolt patterns on the same truck, not when you need a single spare tire to work at all four corners. To level the playing field, NAPCO engineered steel adapters for the rear wheels. These adapters bolted on with the standard six-lug pattern, but sported eight studs on the outside. Now, owners could use matching eight-lug wheels on every corner—problem solved, and a classic case of American engineering doing what it does best: making it work against the odds.

Why Weren’t 1950s 4×4 Pickups Daily Drivers?

So, why didn’t you see a bunch of 1950s four wheel drive pickups dropping kids at school or queued at the grocery store? The answer comes down to practicality and price. These early 4×4 trucks, thanks to the NAPCO conversion, were built with specific off-road needs in mind—think farms, construction sites, and remote backroads, not suburban cruise nights.

For most buyers, the extra capability came at a steep cost—often tacking on over 70% to the base price of a truck. That’s a tall order for someone looking for a family hauler or daily commuter, especially when postwar roads were smoother and two-wheel-drive trucks handled day-to-day chores just fine.

Plus, creature comforts were few and far between. These rigs weren’t built for luxury; they were tools designed to take a beating, not win any beauty contests. So, unless you needed that additional traction, you stuck with simpler, cheaper options that were better suited to everyday life.

From 1956 onward NAPCO’s Power-Pak could be ordered directly from GM factory installed, however in 1960 GM redesigned the front suspension of their pickups so it wasn’t compatible with the NAPCO conversion, and NAPCO and GM parted ways. Shortly afterwards GM started offering their own 4×4 factory option and NAPCO sold their 4×4 business to DANA and faded away.

What Happened to Early 4×4 Pickup Trucks?

So, what ultimately became of those early 4×4 pickups after rough service on farms, ranches, and back roads? Most led hard-working lives, often racking up plenty of miles with their original owners before being handed down or sold to a second (or even third) owner looking for an affordable workhorse.

But once these trucks had given their all—and often after several rounds of patchwork repairs—their journey usually ended at the local salvage yard. There, they were stripped for usable parts, ensuring that even after retirement, a little bit of NAPCO (or a Power Wagon, or a bits-and-pieces Chevy) could live on in other vehicles.