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Backward Glances: Military M-818 6x6 and Shop Trailer From the Vietnam Era

Posted in Features on February 7, 2018
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We’ve all seen them. Maybe you are one! You know, the guy that wheels with every spare part and tool known to man. When a rig breaks, he’s the first one to offer help welding, fabricating, replacing parts, or creatively corncobbing. Those guys deserve a hats-off, and at least a couple of fireside cold ones. However, as impressive as they are, if Marine veteran Tom Price ever shows up with this rig, they will be outmatched.

We all know the military has to operate vehicles in remote country, away from normal parts and repair facilities. Most four-wheelers have done that too, of course. The military prepares by having the means to keep its vehicles up and running no matter what, and this 1969 setup shows how it was done in the Vietnam War era. One thing four-wheelers don’t have is the added “fun” of being shot at, strafed, or bombed.

The truck is one of the legendary M-809 Series 5-ton 6x6s, an M-818 tractor to be exact. The M-809 series was an evolution of the M-39 5-ton truck that appeared in 1951. The M-809 truck came for 1969, and Tom Price’s is one of the early ones. They were offered in 11 main variations: the M-813 cargo, M-813A2 cargo dropside, M-814 long-wheelbase cargo, M-815 logging, M-816 medium wrecker, M-817 dump, M-818 tractor, M-819 wrecker tractor (a rotating crane), M-820/M-820A1/M-820A2 expansible vans, and the M-821 bridging truck.

The Kaiser Jeep M-818 is fully functional and ready to go anywhere at a moment’s notice. It was purchased surplus in 2004 to haul Price’s WWII LVT “Alligator” Amtrack on a lowboy, but it wasn’t quite enough truck and he upgraded to an Oshkosh. At only 16 tons though, the shop trailer is a breeze for the 5-ton! Tom added the ring mount for a .50 caliber M-2 machine gun, something that would only have been seen on a truck operating near the front lines. The early M-39 and M-809 series trucks are very similar in external appearance, but one quick giveaway is the big fender-mounted air filter on the M-809 series trucks. Though not all variations of the M-809 truck had winches, the M-818 did. Standard fording depth is 6.5 feet.

The M-809 series was built by the commercial product division of Kaiser Jeep at first, which became the General Products Division of Jeep Corporation after AMC bought Kaiser Jeep in 1970. It was renamed AM General in 1971, and that entity separated from Jeep in 1983 to become its own company. Updated M-939 versions of this truck built in the ’80s are still in service and on the front lines. Incidentally, the 5-tons were often selected to be gun trucks in Vietnam, where they were used for convoy protection. They hung armor plate all over and mounted enough offensive armament to vaporize anyone stupid enough to attack a convoy.

The 5-ton 6x6 has long been a cornerstone of U.S. military transport fleets. It’s one of those “just-right” sizes that’s big enough for many heavy jobs but small enough to still get pretty far afield. The 5-ton rating is for off-road use. On-road payload capacity is 10 tons. The fifth-wheel trucks are a bit more hampered in cross-country use when hauling a trailer due to the limited angularity of the fifth-wheel, so you aren’t likely to see Tom Price and his truck on Hell’s Revenge at Moab…but you might be surprised at just how far this rig could get up the trail with a skilled and determined driver.

One of the big changes in the M-809 trucks from the older M-39s was the engine. The early trucks had a mix of monster-sized gas engines, diesels, and multifuels. The M-809s all used an 855ci, 240hp Cummins NH250 naturally aspirated diesel. The 855 is one of Cummins’ legendary powerplants and was used in all sorts of applications from trucks to tractors and construction equipment. Later trucks have larger Cummins turbocharged engines but the same power rating.

The shop trailer is 30 feet long and weighs 31,000 pounds. It was rebuilt in the early ’80s and was partially reequipped. You can see the tight, compact layout. The lathe is operated from the forward platform on this side, as is the 17-ton press. The air compressor is seen at the forward end of the platform. The generator/welder sits on the gooseneck. Price’s truck does not have the valve refacer installed; it would have mounted near the acetylene tank.

The Machine Shop Trailer also dates to 1969 originally, but has been updated since. Technically, it was called “Shop Equipment, General Purpose Repair, Semitrailer Mounted.” Instead of having an “M” number, it had a letter designation of SGPRSMD. This one was built by the Southwest Truck Body company, and they were still being manufactured by that company years later. It could be issued to a variety of units, from transportation outfits and artillery units to engineers. An engineer outfit with heavy equipment probably used this one last, as it had some specialty tools geared toward dozers and such.

The trailer has a 12kw, 240V generator with a 100 percent duty cycle that also powers a Hobart dynamotor 200-amp welder. The generator engine is a Hercules D298 six-cylinder diesel. The hydraulically operated clamshell doors can be attached to a tent that completely encloses the shop for cold or inclement weather, and a 60,000-Btu diesel heater is part of the kit. Shop air is supplied by a two-stage electric compressor with a 40-gallon tank. The machine tools carried were somewhat variable, but normally included a lathe with a milling attachment, shop grinders, valve refacer, drill press, 17.5-ton press, 100-ton press, monorail hoist, oxy-acetylene welder, workbenches, grinders, vices, and lots and lots of handtools.

Price, a Vietnam-era Marine, who was a mechanic in the Corps and worked on rigs like this, has a vast and awesome collection of military vehicles—all of a type used by the Marine Corps. Though this particular truck and trailer were issued to the U.S. Army, the Marines used the same equipment, and Price presents them in Marine livery. Down the road, you are likely to see more of Tom Price’s collection here in Backward Glances.

As far as semi trailers go, the shop trailer isn’t huge. Since mobility in rough terrain is a factor with all military vehicles and equipment, making them as compact as possible is important. The fifth-wheel on the M-818 is rated to pivot 21 degrees up, 15 degrees down, and 7 degrees to the sides. Off-road, the fifth-wheel load is rated at 15,000 pounds, but on-road it’s 25,000.

At a Glance
Vehicle: ’69 M-818 5-ton 6x6 tractor
Owner: Tom Price
Engine: 855ci Cummins NH-250 six-cylinder diesel
Power (hp @ rpm): 240 @ 2,100 rpm
Torque (lb-ft @ rpm): 658 @ 1,500
Bore & stroke (in): 5.50 x 6.00
Comp. ratio: 15.8:1
Transmission: Spicer 6453 5-spd
Transfer case: Rockwell T138 2-spd
Front axle: Rockwell, FM240-HX
Rear axle: Rockwell, M240-HX
Axle ratio: 6.433:1
Tires: 11.00-20 NDT
Wheelbase (in): 167
5th-Wheel Payload (lb): 15,000 (cross-country), 25,000 (highway)
Curb weight (lb): 18,100
Fuel capacity (gal): 110
Min. grd. clearance (in): 15
Approach angle (deg): 41
Departure angle (deg): 47.5

On this side you can see the big Powermatic drill press that most of us would love to have in our home shops.
The Hobart welder/generator controls are here. They called it a “dynamotor” because the generator could run the welder or it could operate from an external 240V source using a 50-amp, three-phase motor. The fuel tank holds 55 gallons of diesel. That is one industrial-strength drill hanging to the left of the welder. The white-painted iron pieces are track pin jigs for the big press.
The 100-ton air-over-hydraulic press swings out from the back and the monorail and chain hoist are nearby. Not all shop trailers have the big press. You can also see the mill attachment for the lathe on the wooden crate. Various special toolkits live in the boxes stowed wherever there is space.

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