The B series trucks had a successful production from 1953 until 1966, but they were due for update for driver comfort and safety. Introduced in 1965, the R series production overlapped with the B series to ease the transition for customers. Of the changes between series, the most significant was the introduction of the new cab. While maintaining the same width as the B series, the interior height was higher and the windshield was almost vertical, reminiscent of the L series trucks. The driver's seat was height-adjustable, and there were increased usage of sound deadening materials.

While the B had a more conventional hood and fenders that limited access to the engine bay, the R had a one-piece fiberglass hood that was hinged at the front. This setup is now the industry standard and gave unprecedented access to all of the mechanical components.

Like the outgoing B series, the R series was initially powered by the Thermodyne series of gasoline and diesel engines of 6 and 8 cylinder varieties. By 1966, the new Maxidyne diesel engine had supplanted the earlier engines. Engine codes were broken down as follows: EN - Engine (gasoline), END - Engine Diesel, and ENDT - Engine Diesel Turbocharged, followed by the three number cubic inch displacement.

In addition to the regular R series, Mack developed a cab/hood combination derivative to offer a shorter "Bumper to Back of Cab (BBC)" length, known as the U series. The U had an offset cab, coined the "Commandcab" that placed the drivers side door in the same vertical plane as the side of the trailer. To compensate for the offset cab the engine “doghouse” intruded into the passenger footwell but left the driver's position intact. The U series superseded the C series, with a BBC length only one inch longer (89 vs 90) but with the improvements of the R cab. While the U series was only ever offered as a tractor, the offset cab layout would also be used in the DM series.

The DM was an extra heavy duty version of the U often used in 6X4 construction trucks. Like the RMM, the DMM was all wheel drive, but had not only a short hood/offset cab, but also a set back front axle, requiring a model specific fiberglass hood/fender arrangement.^[5][6]

Mack also developed a RL series lightweight series, primarily as a "western model". The RL made use of significantly more aluminum, including in the frame and other components.

1965–1975 edit

With the introduction of the Maxidyne ENDT-675 in 1966, Mack offered a series of engines that provided better fuel economy and less driver fatigue. The engines produced what Mack called constant-power, with high levels and max levels of horsepower and torque offered at a low and narrow RPM band. This allowed the operator to shift less, lowering the effort needed to drive the trucks.^{[citation needed][clarification needed]}

In addition to the Maxidyne engine, Mack also introduced the Maxitorque transmission.^{[citation needed]}

The RL series was introduced in 1967, and in 1973 the R cab was given a makeover to include a deeper rear wall for more room and a new dashboard design. Additionally, the dashboard was modified to include more plastic components.^{[citation needed]}

1975–1985 edit

The RW Superliner with a large, rectangular hood and grill came in 1977.

1985–1995 edit

By 1988 the numbering system had changed slightly. The prefix “D" and "T”, no longer needed as all engines were diesel and turbocharged, were discarded, as was the "N". The prefix “M” was for “Maxidyne” wide power range models, C was for California certified engines. A “6” was for the 672 cu in (11.0 L) I6, “9” was for the 998 cu in (16.4 L) V8, in 1987 the "7” 728 cu in (11.9 L) I6 was introduced. The next three digits were the horsepower rating of the engine, and an “L” suffix indicated an "Econodyne" low speed model. An example of the difference would be the ENDT673 and later E6-200 being similar engines.^{[2][7] [8]}

The setback front axle RB was introduced in the 1990s.

The RD was given a new more aerodynamic nose in 1991, with square sealed beam headlights. The other R models would continue with the '65 era nose until they went out of production.

1995–2004 edit

The RD/RM ended production in late 2003 as a 2004 model. The RB and DM were scheduled to be built into 2004.^[9]

Legend Special Edition edit

A small series of "R-Model Legend" models were built at the end of the RD/RM production run. These models, announced by Mack in 2003, included a special steering wheel, limited edition paint, badges chrome and embroidered seats.^[10] Mack was reported to have planned to make 100, but it is unclear how many were actually built.^[9]

Mack utilized the cab of the R in a variety of ways beyond the R itself. With the B series still in widespread use in the late 1960's, Mack offered a B to R upgrade for the cab and front sheet metal. This allowed operators to keep the mechanical portions of the older truck that may have not needed replacement and marry them with the much improved cab of the R. It is unclear of how many of these kits were sold and installed.^{[citation needed]}

Truck manufacturer Brockway also used the R cab on their 700 series Husky line of trucks in the mid-70's, which is often attributed as one of the reasons that Brockway went out of business. Brockway was attempting to expand market share, competing directly with its parent company Mack and having a vehicle with the exact same cab did not help the smaller company differentiate itself.^{[citation needed]}

R-11 Refuler edit

In conjunction with the US Air Force, Mack built a prototype heavy-duty hybrid electric av gas refueler in 2005. This RD utilized the hybrid engine to reduce fuel costs and emissions. According to the Air Force, "The vehicle operates with a diesel engine, an electric motor and a battery pack to optimize fuel efficiency. After the hybrid is started, the electric motor, which draws stored electricity from the battery pack, is used to get the vehicle up to speed, the lieutenant said. Once the truck is at an optimal speed, the diesel engine takes over. The battery pack restores energy by a regenerative braking process. The system captures energy that is lost during the driver's "stop and go" process."^[11]

In addition the US plants, Mack produced the R model (and some derivatives) in both Australia and Iran.

Australia edit

Iran edit

Iran Kaveh established ties with Mack in 1963 to produce licensed built trucks including the R. Approximately 60% of the content being Iranian sourced. Specifications and design of the R were modified to be suitable to Iran.^[12] With over 98% of the heavy duty trucks in Iran being Mack's, either being produced locally or imported, the fall of the Shah in 1979, Iran Kaveh put an end to sales of new Mack's in the country. It was estimated that in 1987 there were between 35,000 - 55,000 Mack trucks operating in Iran.^[13]

Mack Trucks of Canada also sold a few oil-exploration rigged RD models to Iran in 1987, as the US had sanctions in place that would now allow trade between the two countries.

• R - Standard model
• RB - Set back front axle (except in New Zealand - see NZ Mack RB)
• RD - Heavy Duty R
• RM - 4x4 Municipal/maintenance chassis
• RMM - 6x6 Municipal/maintenance chassis
• RS - Western R series, S (steel frame)
• RL - Western R series, L (aluminum frame)
• RW - Western series, replaced by the Mack Super-Liner
• U - Short hood offset cab
• DM - Heavy-duty U
• DMM - All wheel drive DM
• Chassis numbers (GVW Rating):
  • 4xx -
  • 6xx -
  • 7xx -
  • 8xx -

Note: the xx is the place holder for the engine code.

• Suffix letters:
  • T - Tractor
  • S - Six wheel chassis
  • L - Light weight components
  • X - Extreme duty

•  
  R refuse truck
•  
  R semi-tractor
•  
  RD dump truck
•  
  DM mixer truck
•  
  DM dump truck with snowplow
•  
  U-model with offset cab

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