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Wagging the (bull)dog: on the road in the auto Mack Magnum


kscarbel2
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Commercial Motor / October 22, 1998

Commercial Motor recently drove a left-hand drive Mack-badged Magnum demonstrator around Allentown, Pennsylvania; home of Renault's subsidiary. This was no ordinary Magnum, having been converted by Mack into a 6x4 using a Hendrickson air-sprung Eaton rear bogie (to the US passion for double drive) and fitted with a nine-speed Eaton AutoShift automated manual transmission (AMT) in place of the regular RVI B18 synchronized manual box.

By US standards the Magnum is a heavyweight, US truckmakers build far lighter 6x4s, and this has put off operators on the truck show circuit. However, drivers love its flat floor interior and roomy interior, along with its European level of comfort. And all the Magnum's positive attributes, including a commanding view and excellent ride, are as true in the US as they are in Europe. But the Eaton AutoShift makes it just a bit different.

Commercial Motor has already reported on the European version of AutoShift, based on Eaton's 16-speed synchronized manual box, so it was interesting to see how a US market 9-speed AutoShift works. As in the installation in the MAN F2000, which has a column selector, our Magnum had a floor mounted lever like a conventional Allison auto box. On AutoShift, the clutch is retained for pulling away and stopping; for all other changes the box works automatically, synchronizing gears and selecting the appropriate ratio.

On the European version, the driver keeps his foot on the pedal and changes are made depending on throttle position and engine load. In the Mack, as each gear change was signalled to the driver by a bleeper, we had to lift off throttle and look at the rev counter needle dropping till the next gear 'caught", before pressing down on the pedal. This felt rather like Eaton's old SAMT.

Also we understand the US AutoShift we drove was an early version, and later versions will behave like their European cousins. Either way, AutoShift is very driver friendly. If you want to make your own shifts, you simply press the up or down command buttons on the selector lever.

While the manual clutch delivers low-speed control, considering how well ZF has managed without it in its AS-Tronic box, we reckon that AutoShift would be just as effective as a two-pedal system. Based on our brief drive, the 9-speed AutoShift works just as well as its 16-speed stablemate. Changes were smooth and progressive, and well matched to the 460hp Mack E7 12litre engine, prompting the question: why not offer a 9- or 13-speed Roadranger-based AutoShift box in Europe? Not the least in a Renault Magnum!

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