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We’re introducing a new feature series at Diesel Army that will showcase some of the coolest military vehicles on four (or more) wheels. While there’s no shortage of awe-inspiring vehicles and modifications available to the general public, as we all know Uncle Sam has some of the most interesting stuff around, and that hardware is often hard to come by for the general population.
Part of the M939 series of trucks originally produced by AM General, later A2 versions like this one were built by Bowen-McLaughlin-York. Cargo variants like this M923A2 measure 25 feet and seven inches in length, eight feet, and two inches in width, and nine feet, eight inches in height. This particular truck is even longer than that, as the front bumper has been extended to install an additional storage box.
This month, we’re taking a look at Rob Dicarlo’s BMY Harsco M923A2. This five-ton, 6×6 heavy-duty transport hails from the Desert Storm era. Built in 1990, this particular model spent its early days hauling around the 105 mm Howitzer cannon and its ammunition at the National Guard base in Walnut Creek, California, in the 79th IBCT 1st Battalion 143rd Field Artillery Regiment.
One of the key features of the A2 variant is the central tire inflation system (CTIS). This system provides control over the air pressure of each tire on the fly in order to improve its performance over varying surfaces, thereby substantially increasing the truck’s maneuverability. The CTIS also allows the driver to maintain air pressure in the event of a puncture so that the vehicle can still be driven with a slow leak. Considering the fact that each one of these tire and wheel combinations weighs several hundred pounds a piece, this functionality is vital out in the field.
“I have been an avid off-roader my whole life and I just wanted something different that could handle lots of off road use, yet would be comfortable to drive,” Rob said. “Having a six-wheel drive off-road toy on 50-inch tires is the ultimate ‘go anywhere’ vehicle. Another plus is that the CTIS (central tire inflation system) means there’s no need to get out to change tire pressures, and if you get a puncture you can put the system in run-flat mode and keep driving.”
Rob Dicarlo has done a number of modifications to this M923A2 to make it more user-friendly, including an upgraded air conditioning system, overhead radio, CB mount, and additional boost and EGT gauges. Gear selection is courtesy of an Allison five-speed automatic that's hooked to a two-speed transfer case. The front axle is engaged in low range.
Derived from the M939 transport truck, which was developed in the late 1970s to replace the aging M39 and M809 series and is still in production today, this M923A2 weighs in at about 22,000 pounds and is powered by an 8.3-liter, six-cylinder turbocharged Cummins diesel motor that currently generates about 375 horsepower and 1,000 pound-feet of torque – a substantial upgrade from the 240 hp and 716 lb-ft these motors make in stock configuration – while still returning 14 to 16 miles per gallon in its present tune. To get the power to all four corners, the motor is hooked to an Alison five-speed automatic transmission and a two-speed transfer case.
This turbocharged, 504 cubic-inch Cummins 6CTA8.3 motor has been substantially warmed over to provide significantly more power than it did in its stock configuration, yet it still yields fuel economy numbers in the teens according to Dicarlo. Not bad for a truck weighing 11 tons.
M923 variants of the M939, such as the one we’re looking at here, were specifically configured for cargo transport and featured a body with drop sides so it could be loaded from the side by forklifts.
“The driver who was in charge of maintaining this vehicle during its time in the service received an award for zero failures in over 100,000 miles of use,” explains Bill Dozer of Those Military Guys in Rancho Cucamonga, California, who specialize in maintaining vehicles like the M923A2. “It was kept at the National Guard base due to the fact that it was one of only two M923A2 trucks on-base.”
To help the Cummins breathe more easily, Dicarlo installed a custom air cleaner kit and a ram air scoop.
Far from a show piece, this M923A2 has seen plenty of off-road hours at locations ranging from vast expanses of desert to snowy mountain trails and has dispatched four-foot deep water crossings and extremely deep mud bogs with aplomb.
The truck’s suspension design consists of a leaf spring front end and floating tandem rear axles. Generally, full floating axle designs are reserved for vehicles that are built for severe duty or heavy hauling, and the M923A2 fits the bill for both. This type of axle uses an axle shaft on each side that is either splined at both ends or splined on the inner end, and has a drive flange on the outer end.
As capable as the M923A2 is, Rob has made a number of modifications along the way to improve his vehicle. Like most builds, this project may never be “done,” as he is constantly finding ways to step up the truck. “There are so many upgrades I just can’t even remember them all,” he admits. “The truck is getting additional modifications on a regular basis. The motor alone has had numerous hours of tuning to get the power where it is.”
Although it maintains a stock appearance, the M923A2 has received numerous upgrades to improve its already admirable capability, including custom seats that are designed to look like the factory pieces, a rear under-bed 18,000-pound Warn winch, and an overhead light bar comprised of six HID lights and two infrared night vision lights.
It’s clear from Rob’s sentiments about his M923A2 that the project is a labor of love. “Like most men, I subscribe to the idea that big boys want big toys.”
And, if you’re going to go big, what better way to do it than with a vehicle purpose-built for the job? Stay tuned next month for our next installment of Monthly Military.
