The Mack U series was a cab-and-hood derivative of the R series, built to shorten the bumper-to-back-of-cab length. Its trick was an offset cab, called the Commandcab, that put the driver’s door in the same vertical plane as the side of the trailer.
Mack U series at a glance
| Maker | Mack Trucks |
|---|---|
| Family | derivative of the Mack R series |
| Cab | offset Commandcab |
| Driver’s door | in the same vertical plane as the trailer side |
| Engine layout | doghouse intrudes into the passenger footwell |
| Bumper-to-back-of-cab | 89 in, against 90 in for the C series it replaced |
| Body style | tractor only |
| Layout passed to | the DM series |
The U series is described in the development section of the English Wikipedia article on the Mack R series; there is no dedicated U article.
History of the Mack U series
American length rules made the bumper-to-back-of-cab measurement, the BBC, as important as the engine size: every inch saved in front of the trailer was an inch of payload behind it. Mack’s answer in the R family was the U series, a cab-and-hood combination that cut the distance from the bumper to the back of the cab.
The key to the U was its offset cab, which Mack called the Commandcab. Instead of sitting centrally, the cab was moved so that the driver’s door was in the same vertical plane as the side of the trailer — useful when the driver had to step out beside the load. To make room for the engine, a doghouse intruded into the passenger footwell while the driver’s position stayed where it was. The U replaced the earlier C series with a cab only one inch longer, 89 inches against 90, but with the improvements of the new R cab, and it was offered only as a tractor. The offset layout proved useful enough that Mack used it again in the DM series, the extra-heavy-duty construction truck.
Design and features
- Offset Commandcab: the driver sits close to the trailer line, with the engine doghouse beside the passenger.
- Short BBC: 89 inches, one inch longer than the C series it replaced.
- Tractor only: the U was never built as a straight truck.
- R cab benefits: taller interior, height-adjustable seat and more sound deadening.
Mack U series versions
- U series: the offset-cab short tractor.
- U600: the model designation recorded in this collection.
- DM: the extra-heavy-duty development of the same layout.
The U was derived from the Mack R series, and its layout went on to the Mack DM series. The conventional R itself and its construction versions are described on the Mack RD series page. More trucks are in the Mack collection.
Sources
- Mack R series, English Wikipedia: the U series, Commandcab, BBC length, the DM
