The M35 'Deuce and a Half': History, the Multifuel Engine, and Why It's Called the Whistler

An M35A2 6x6 cargo truck, the classic "Deuce and a Half." Photo: Alf van Beem, public domain (CC0), via Wikimedia Commons.

Few military vehicles have earned as many nicknames, or served as long, as the M35. Known universally as the Deuce and a Half, and to different generations of soldiers and mechanics as the REO, the Eager Beaver, and the Whistler, this 2½-ton 6x6 cargo truck has been in continuous production and service since 1950 — an astonishing run for any military vehicle. Here's the full story of where it came from, what made it tick, and why it earned every one of those names.

Where the M35 came from

The M35 was developed by the REO Motor Car Company starting in 1949, entering service in 1950 as a 2½-ton, three-axle 6x6 truck intended to replace the earlier World War II-era GMC CCKW. It's that older CCKW, in fact, that the M35 inherited its most famous nickname from — Deuce and a Half simply refers to the 2.5-ton payload rating both trucks shared, and the name stuck fast to the M35 as it took over the role.

The truck is also widely known simply as the REO, after its original manufacturer, even though production later passed to Studebaker, Kaiser Jeep, and finally AM General as the design was continually updated and re-contracted over the decades. In its early years it also picked up the nickname "Eager Beaver", a reference to its genuinely impressive fording and off-road capability straight out of the factory.

What TUL and A-series designations mean

The base M35 was joined by the M34 (an earlier, slightly different variant) and the M36, an extra-long wheelbase version with a 16-foot cargo bed. As the design was updated over the decades it picked up suffixes: M35A1, M35A2, and eventually M35A3, each revision bringing engine, electrical, or drivetrain updates while keeping the same basic chassis and role.

The multifuel engine — and why it's called the Whistler

A 1971 AM General M35A2 fitted with a winch. Photo: Guy.cooper, CC BY-SA 3.0, via Wikimedia Commons.

The single biggest change across the M35's life was the move from a petrol engine to the multifuel engine fitted to the M35A2 onward. The multifuel LDT-465 series, built by Continental, was designed to run on diesel, petrol, jet fuel or kerosene without modification — a deliberate piece of Cold War logistics thinking, since it meant a single truck could keep running on whatever fuel was actually available in a given theatre, rather than depending on one specific supply chain.

This is also where the M35's most distinctive nickname comes from. Later multifuel variants were fitted with a turbocharger, the 3LJ319, which produced a very distinctive, high-pitched turbo whine under load — loud enough that soldiers and mechanics started calling any turbocharged multifuel M35 a "Whistler." A later, quieter turbo unit (the 3LM39) was fitted to some final-production engines and doesn't produce the same sound, so strictly speaking not every late multifuel M35 is a true Whistler — but the nickname has stuck to the model as a whole regardless.

The many configurations of the M35 family

What makes the M35 genuinely remarkable is how many different jobs it was adapted to do, all built on the same basic chassis and drivetrain:

• M35/M35A1/M35A2/M35A3 cargo truck — the standard troop and cargo carrier, the version most people picture
• M36 long-wheelbase cargo truck — the extended 16-foot bed variant for bulkier loads
• M44/M45/M46 chassis — designated the long single tandem, long double tandem, and extra-long double tandem chassis used as the basis for specialist bodies
• M49 fuel tanker — built on the M45 chassis, carrying a 1,200-gallon fuel tank in either a triple-compartment or twin 600-gallon baffled configuration
• M50 water tanker — a 1,000-gallon water tank version, later variants gaining internal baffles to control weight transfer while moving
• M109 shop van — a mobile workshop body, used for field maintenance and repair work
• Dump truck variants — for engineer and construction units
• Wrecker/recovery variants — fitted with a crane or boom for vehicle recovery work
• Tractor variants — configured to pull trailers and towed equipment rather than carry cargo directly

Add to that the drop-side "C" suffix cargo variants (M35A2C, M36A2C) and you get a genuine family of vehicles all sharing the same running gear — which is exactly why the M35 became so easy for REME-style workshops and civilian restorers alike to maintain across such a wide range of roles.

Why it's still relevant today

Decades after the last M35 rolled off a production line, the type remains hugely popular with overlanders, vehicle restorers, and collectors, largely because of the same qualities that made it a success for the military: a simple, rugged drivetrain, straightforward mechanicals that don't rely on delicate electronics, and a spares network that, thanks to the sheer number originally built, is still very much alive today.

If you're restoring or maintaining an M35, our Military Vehicle Spares & Accessories range covers parts and consumables for exactly this kind of vehicle, and we currently have a genuine M35A1 US Army REO in stock for anyone after the real thing.

Frequently asked questions

Why is the M35 called the Deuce and a Half?
Deuce and a Half refers to its 2½-ton payload rating, a nickname inherited from the earlier World War II-era GMC CCKW truck that the M35 replaced.

Why is the M35 called the Whistler?
Later multifuel M35A2 variants were fitted with a turbocharger (the 3LJ319) that produced a distinctive high-pitched whine under load, earning the truck the nickname "Whistler."

What is a multifuel engine?
A multifuel engine, like the Continental LDT-465 fitted to the M35A2, can run on diesel, petrol, jet fuel or kerosene without modification, giving military users flexibility over whatever fuel supply was available in the field.

What variants did the M35 come in?
Beyond the standard cargo truck, the M35 family included the long-wheelbase M36, fuel and water tankers (M49/M50), a mobile workshop (M109), dump trucks, wreckers, and tractor units, all built on the same basic chassis.

What does REO mean on an M35?
REO refers to the REO Motor Car Company, the original manufacturer that developed the M35 from 1949 — production later passed to Studebaker, Kaiser Jeep and AM General.