Mack Trucks in military service

Mack Trucks has been selling heavy duty trucks and busses to the US military since 1911. Virtually every model has been used. The majority have been commercial models designed and built by Mack with their own components, but they have also designed and built military specification tactical trucks and other customised vehicles.

World War I
Before the US entered the war the Army had used small numbers of Mack trucks in trials. The commercial AC, designed with US Army input, was introduced in 1916. First purchased by the UK, it was an immediate success in military service.

AC
The model AC, with its well known tapered hood, was introduced in 1916. A 4X2 with chain drive, it was strong, reliable, and worked well in rough terrain. It had a 471 cuin L-head I4 with 40 hp. Over 2,500 $5 1/2$(3,175 kg), $7 1/2$(4,990 kg), and $3 1/2$(6,804 kg) ton trucks were built for the UK and US military. The US Army made it the only standard truck over 5 tons (4,536 kg).

AP
The model AP, introduced in 1926, was an 8 ton (7,257 kg) 6x4 similar to but larger than the AC. It had a 706 cuin L-head I6 engine that developed 150 hp at 2,000rpm. In 1929 the US Army bought them as prime movers and tank carriers.

World War II
In 1940 the British began buying Macks; when the US entered the war all production was for US and Allied militaries. In addition to commercial models Mack also designed and built a large number of tactical trucks. Because of their proprietary, rather than common standard, design, many were exported to US allies. Tank transmissions and marine diesels were also manufactured. By the end of the war Mack had supplied over 32,000 trucks and other components worth over $3,000,000.

E Series
The E series was introduced in 1936 as a conventional or cabover 4x2 truck; larger models were also available as semi-tractors. It was a modern design, with a closed cab, roll up windows, and auto type styling. Early models had an EN310 310 cuin L-head I6 engine developing 90 hp. Later models could have the larger EN354 354 cuin engine developing 110 hp at 2,620rpm and 254 lbfft at 1,200rpm.

By 1940 the US Army and Marines were using $5 1/2$ ton (2,268 kg) EE dump trucks, EH 5 ton (4,536 kg) fuel tankers, EHU cabover wreckers, and other specialty vehicles. Early models were standard commercial models, with chrome trim and hubcaps, in 1942 all trucks became plainer.

The military model EH was a 5 ton (4,536 kg) 4x2 cargo truck. The EH, EHU (cabover) and semi-tractor models EHT and EHUT had EN354 engines and disc wheels. Early trucks had standard commercial cabs, later open military cabs were used. Of 3,500 EH and 50 EHT built in 1943–1944, over 2,400 were exported to the British.

L Series
The L series, introduced in 1940, were commercial design heavy duty trucks larger than the E series.

The LMSW 10 ton (9,072 kg) 6x4 chassis was adapted for military wreckers in North Africa. Their EP 611 cuin OHV I6 developed 160 hp. They had wide tandem rear axles so oversize 14.00x20 single rear tires could be used. Models 23 (193) and 39 (181) went to the British, models 53 (130) and 57 (160) went to the Canadians. The primary difference between the models was their bodies, Model 57s also had an open cab. They were shipped partially knocked down, with the cab, chassis, and body shipped separately and assembled at their destination. All Model 39s were shipped to India for use in the Far East.

The LPSW was a $7 1/2$ ton (15,876 kg) 6x4 dump truck. Intended for the Panama Canal, some were sent to the British for use in the Pacific theater. They had a 12 cubic yard (9.17 cubic meter) rear dump body and an open cab with a windshield on the left half only.

NJU Semi-tractor
The NJU (G-639) was a military design 5 ton (5,443 kg) 4x4 semi-tractor used to tow bridging pontoons and equipment. Their 532 cuin developed 136 hp at 2,400rpm. Unlike most semi-tractors, all but 8 NJUs had a large toolbox behind the cab to carry outboard engines and other tools used in bridge building. 8 NJU-2s were used for communications trailers and had no toolboxes. Several other manufactures built standardized models of similar trucks, so only 700 NJUs were produced in 1941–1942.

NM Series
The NM series was Mack’s first tactical military vehicle. A 6 ton (5,443 kg) 6x6, they were used for hauling AA guns and crews. Their EY 707 cuin OHV I6 engine developed 170 hp.

Models 1, 2, and 3 had the enclosed cab from the commercial L-model and commercial tires. Models 5, 6, 7, and 8 (there was no NM-4) had open cabs and military non-directional tires. Other than cabs and tires, NMs had only minor detail differences. Over 8,400 of all models were built in 1940–1944.

NO Series
The NO series were military design $2 1/2$ ton (6,803 kg), 6x6 artillery prime movers meant to tow the 155mm "Long Tom" field gun, 8 inch howitzer, and 240mm howitzer (the 240mm howitzer was two separate loads). They used the same EY 707 cuin OHV I6 engine developing 170 hp as the NM series. The NO-2, −3, −6, and −7 varied only in details (NO-1, −4, and −5 were single prototypes). 2050 production NOs were built in 1943–1945, all 1097 NO-3 and −6 models were exported.

NR Series
The NR series (G528) were 10 ton (5,443 kg) 6x4 cargo trucks similar to the L series. An ED 519 cuin diesel I6 developed 131 hp. Originally intended for British use as light tank transporters in North Africa, they had wide rear tandems so that oversize 14.00x20 single tires could be used. 90 NR1 had cabs of the obsolete EX, models NR2 to NR7 had L series cabs, NR8 and later had open cabs. Other differences between models were body types, some components, and minor details. All were exported as partly knocked down, with the chassis, cab, and body shipped separately then assembled at their destination. Unlike most US trucks they had diesel engines, making them valuable for long distance trips. Over 15,000 were built between 1940 and 1944, the most of any series.

1945 to 1965
In the 1950s Mack built US standard tactical trucks, as well as supplying commercial models for non combat roles.

M54 Series
The M54 (officially M39) series (G-744) was a standardized military design 5 ton (4,536 kg) 6x6 chassis, with many models. A Continental 6606 602 cuin developed 224 hp and 504 lbfft. In 1952 Mack began building the M51 Dump (4,310), M52 Semi-tractor (1,443), M54 Cargo (1,126), M55 Long cargo (85), and M61 Chassis-cab (107). In 1962 they took part in program to retrofit some of the series with Mack ENDT 673 673 cuin turbocharged diesel engines developing 211 hp and 610 lbfft. Inside two years, after 2,500 conversions, the Army standardized the Continental LDS-465-1A engine.

M123 and M125
The M123 & M125 (G-792) were standardized military design 10 ton (9,072 kg) 6x6 semi tractors and artillery prime movers. Designed by Mack, they used many components from the NO series. Mack built 392 M123s, used with a lowboy trailer to recover and transport tanks, and all 552 M125s, between 1955 and 1957. Later follow-up orders called for 420 M123s and retrofitted 210 more with Cummins engines.

B Series
The B was Mack's conventional series from its introduction in 1953 until 1965. They were not widely used by the US military, but the US Navy did buy some in 1955. The B71ST were commercial 6x4 semi-tractors. A Cummins NH diesel I6 developed 200 hp at 2,100rpm.

1965 to 2005
In 1966 the R and similar DM series conventional commercial design were introduced. The US military used many off the shelf models. Trucks sold overseas were often sold with military options, one of the most popular was the sheet metal hood and fenders (also available on commercial models). Both R and DM were available with full time all wheel drive, the RM and DMM.

DM400
The DM492S was a 5,000 usgal 6x4 aircraft refueler. A mid-range Caterpillar 3208 636 cuin V8 developed 225 hp at 2,800rpm. The US Air Force ordered 1,010 in 1980.

R600
The R611ST was a typical 6x4 commercial design semi-tractor. A ENDT673 673 cuin diesel I6 devoloped 225 hp at 2,100rpm. The ENDT673 (later renamed E6) was used in most R and DM models.

RD600
The RD6866SX (MC3) was an 8-ton (7,257 kg) 6x6 tactical truck. An EM6 Maxidyne 673 cuin diesel I6 developed 285 hp at 1,800rpm. The Australian Army ordered 940 with delivery starting in 1982. They had right hand drive and were assembled in Australia. Cargo, dump, prime mover, wrecker, fuel tanker, water tanker, bridging, and concrete mixer models were built. The asphalt distributor was a 6x4. The cargo models often carry one APC and tow a full trailer carrying another APC. Containers can also be carried, and some have a self-loading crane between the cab and body.

2005 to 2015
With the end of R/DM production in 2004–2006 the successor Granite series has been offered with military options. Mack is also involved in the Sherpa line of medium armored cars and supplies components for military service.

Granite Series
The Granite GU813E is a 6x4 personnel carrier. A MP8 13-Liter diesel I6 develops 400 hp and 1460 lbfft. A semi-tractor, wrecker, fuel tanker and water tanker are offered. The similar Vision is offered as a semi-tractor with sleeper cab.

Sherpa
The Sherpa Carrier is a 2 to 4 ton (1,814 to 3,629 kg) 4x4 armored cargo truck. A Turbodiesel I4 develops 215 at 2,300rpm and 590 at 1200–1700. It is also offered as a 4-door personnel carrier, an open roof model, and a lightweight 105mm howitzer carrier.