Auto Shift To Save Fuel
Spec'ing automatics can also result in savings on driver recruiting, training and retention costs.
Tom Berg
Equipment Editor
Transmission automation has always had the stigma of higher fuel bills. But 'taint so, says everyone associated with truck sales. In fact, with the new 2004 engines, the fuel curves are less forgiving and require more skill from the driver to keep the revs just so. An automated box can help the less skilled — less economical — shifters get close to the fuel economy of the top drivers who know how to jam those gears just right.
According to Charlie Allen, who is responsible for sales of the ZF Meritor FreedomLine automated mechanical, fleets typically improve fuel economy by 5% by using automated trannies. That could go a long way to offsetting fuel penalties of the new, low-emissions engines.
Another benefit is in driver recruiting. Automatic transmissions are undoubtedly much easier to drive than the constant-mesh manuals in heavy trucks, so inexperienced people can be recruited to fill seats. In certain jobs, automatics can pay for themselves in less maintenance and longer life for the engine and driveline. Fuel economy can be better for even the good driver, because while the driver may get tired, the transmission never does, and always shifts properly. And they can reduce driver turnover, producing hidden savings to help offset the significant price differential over a manual.
But even without the driver savings, fuel alone can pay for the transmissions in two years. So while automatics only account for about 10% of the heavy truck market today (50% for mediums and 95% for light trucks), Class 8 fleet managers might seriously consider spec'ing automatics in their next truck order.
New products are now available from several manufacturers, and greater competition in heavier classes has brought down prices. First, let's look at the types:
• Fully-automated, continuous power — A generic description of Allison automatics, which are related in principle to those on cars and light trucks but are much stronger and more complex. Allisons use hydraulic pumps, torque converters, gear packs and electronic controls to transmit power. Power flows through continuously during operation.
Allison has phased out its old AT (for light-medium trucks), MT (for medium trucks) and HT (for heavy trucks), though many are still on streets and roads. These have four or five speeds, with top gear being a direct, 1 to 1 ratio. This limits top speeds on highways, so most worked better on city streets and rural roads. Most were built with hydraulic controls, but later models had electronic controls.
In truck applications, Allison's lineup includes Highway Series (HS), and Rugged Duty Series (RDS), in addition to emergency, motorhome and bus transmissions. They are then classified by torque capacity up to the 4500 model and have four, five or six speeds. When present, 5th and 6th are overdrive ratios. The 1000, 2000 and 2400 series products are for light- to medium-duty trucks. These have five speeds with an overdrive; the 1000 has a parking pawl within the transmission, and others have a Park position that actually applies a parking brake.
• Automated, interrupted power (also called automated mechanical) — Describes Eaton Fuller's AutoShift, whose electronic controls work with the engine's to select and change gears in a mechanical gearbox. Engine power is interrupted during shifts. Automation can be full or partial, as with other products from Eaton Fuller and its competitors: Fuller's Top 2, and ZF Meritor's Engine Synchro Shift are examples.
All need a manual clutch to disengage the engine from the transmission while stopping and starting out. Once under way, automation of some or all shifting is done without the clutch. This is called the "three-pedal" type of automated transmission, because the driver still needs to punch a clutch pedal, but far less often than with a straight manual transmission.
There's no clutch pedal with Eaton's 6- and 10-speed UltraShift, Mercedes-Benz's 6-speed Automatic Gear Shift and ZF Meritor's 12- and 16-speed FreedomLine, so they're called "two-pedal" products. An automatic clutch engages and disengages when commanded by the transmission's electronic controls. The driver operates the transmission pretty much like an automatic. However, the clutch can be abused; one way is if the driver uses the throttle to hold the truck from rolling backward at an uphill stop. So drivers still need to know what a clutch is, and how to avoid "beating" it.
Eaton's Lightning and ZF Meritor's Engine Synchro Shift are mostly manual, but electronics help the driver downshift and upshift without having to manually match engine and gear speed. The earlier Eaton Top 2 operates only the transmission's two highest ratios, so is useful for over-the-road trucks. Such products cost only a few hundred dollars more than a straight manual gearbox.
The more the automation, the higher the price. A heavy duty Allison costs $8,500 to $11,000, though Allison reps might go lower if potential customers lay out direct challenges from Eaton or ZF Meritor products. Those are $5,000 to $6,000 options over a manual transmission. Medium-duty products cost less, of course.
If you think you can never pay off the cost of an automatic or automated transmission, you might think again. Truck operators who use Allisons testify that they save considerable money in recruiting, training and retention. For instance, half the drivers at a Texas dump truck fleet we heard about are women, most of whom would never have considered driving trucks for a living. Women are generally gentler on the equipment, which saves maintenance money.
Eaton's AutoShift is also at work on and off-road. U.S. Xpress Enterprise's entire fleet now has them, and executives say recruiting is much easier because of it. However, we once met a woman who said she drove for the fleet but didn't like their transmissions because "I want to be in control of the truck, and I couldn't with that thing." them.
We've gotten glowing reports on the value of ZF Meritor's FreedomLine, which operates smoothly and always picks the right gear. For now it's approved only for on-road trucks, as ZF, which makes most of the product in Germany, has not yet OK'd it for off-road use.
Scott Heller Trucking, a dump truck operation in Missouri, uses AutoShifts, and finds they offer many of the benefits of Allisons. One drawback, however, is limited speed in reverse. This has prompted a few drivers to try to force the transmission into high range, which can be done with a manual Roadranger, but not with the AutoShift. The result was three expensively damaged gearboxes.
So there are advantages and drawbacks to automatic and automated products. Get a lot of advice from actual users before you make a choice.
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