The ZF Freedomline automated tranny.

You’ve probably got an automatic in your car or pickup truck, but it’s likely the big truck you drive has a manual. That’s changing, with about 10% of heavy duty trucks now spec’d with automatics of some kind, and more than half of all medium-duty trucks. Both percentages are growing, for sometimes obvious reasons.

Automatic transmissions are much easier to operate than manuals, so you don’t need as much experience to drive a truck. This helps fleets with recruiting and training. In certain jobs, automatics can more than pay for themselves in terms of maintenance and longer life for the engine and driveline. Fuel economy is usually better because – while you may get tired – the transmission never does and always shifts properly.

New products are now available from several manufacturers, and competition has lowered prices. Allison, the grand daddy of commercial truck automatics, has drastically cut prices on most of its products. A heavy duty Allison now costs about $8,500 over a manual, while medium-duty Allisons now cost from $1,600 to $3,200 – in some cases, half their former prices. In general, price premiums for automated mechanical transmissions range from a few hundred dollars to about $6,000 over a standard manual.

Picking the right products for the job requires knowing what they are and how they operate. So let’s look at the types of transmissions now available:

• Fully-automated, continuous power – A generic description of Allison automatics, as well as Aisen automatics in some imported trucks. These are related in principle to those on cars and light trucks but are much stronger and more complex. Full automatics use hydraulic pumps, torque converters, gear packs and electronic controls to transmit power. Power flows continuously, even during shifts.

Allison’s old AT (for light-medium trucks), MT (for medium trucks) and HT (for heavy trucks) are out of production, but many are still on the road. These have four or five speeds, with top gear being a direct, 1-to-1 ratio. This limits top speeds on highways, so these worked better on city streets and rural roads. Most were built with hydraulic controls, but later models had electronics to control shifting.

Allison’s current World Transmissions, comprising MD (medium duty) and HD (heavy duty) models, use four, five or six speeds. When present, 5th and 6th are overdrive ratios. Allison also has the 1000, 2000 and 2500 series products 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 in the driveline or at the rear wheels.

• Automated, interrupted power – Also called automated mechanical, this term primarily describes Eaton Fuller’s AutoShift and UltraShift, ZF Meritor’s FreedomLine, and Mercedes-Benz’s Automatic Gearshift, or AGS. These do all the shifting, with electronic controls on transmission and engine working together to select and change gears in a mechanical gearbox. Engine power is interrupted during shifts.

The AutoShift has a manually operated clutch and clutch pedal – a so-called three-pedal system. The clutch is needed only when starting out from a dead stop and when coming to a halt. UltraShift, FreedomLine and AGS have automatic clutches and no clutch pedal – so-called two-pedal systems. The clutch engages when needed. In Eaton products, that’s only when starting out and stopping, because the gearboxes are float-shifted. The European-designed ZF Meritor and M-B products use the clutch for every shift.
Full Or Partial Automation

All the above products are fully automated because the tranny will completely shift by itself, unless you tell it to up- or downshift or to stay in a certain gear. Most drivers at first want to prompt a lot of shifts themselves, but they soon learn that the tranny almost always picks the correct gear and does a better job if just left alone. An exception is drifting down a long grade; here you’ll probably want to tell the tranny to downshift to bring up engine revs so the engine brake can work harder.

There are also partially automated products, such as Eaton Fuller’s Top 2 and Lightning series, and ZF Meritor’s Engine Synchro Shift, or ESS. Those use a manual clutch, but help with some of the shifting work. The Top 2 shifts between the top two gears while the truck is cruising on the highway, while the Lightning and ESS will rev or slow the engine to assist with double-clutching.

Eaton’s two-pedal UltraShift comes in a 6-speed for midrange trucks and a 10-speed for heavies. Its three-pedal AutoShift’s main product is a 10-speed, and there are multi-speed models too. Meritor’s heavy duty FreedomLine comes in 12- and 16-speed versions. Mercedes-Benz’s AGS for medium-duty trucks is a 6-speed.

All automated mechanical transmissions are driven pretty much like an automatic, but its clutch can be abused. One way is using the throttle to hold the truck from rolling backward at an uphill stop, causing the clutch facing to slip and burn. So you still need to know what a clutch is, and how to avoid “beating” it.
Preferences And Economics

All modern Allisons shift smoothly and feel pretty much like the transmission in your car or pickup. Allisons are especially good in heavy traffic and off road. Automated mechanical transmissions feel like a manual because they’ve got regular gearboxes. You can feel the tranny changing gears and the engine revving up and down, and the truck sounds like its driver is a real pro.

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 more gentle 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.”
So not everybody likes them.

We know of one dump truck operation in Missouri that uses AutoShifts, and its owner finds they offer many of the benefits of Allisons. But one drawback is limited speed in reverse; this has tempted a few impatient drivers to try to force the transmission into high range, which can be done safely with a manual Roadranger, but not with the AutoShift. The result was expensive damage to several gearboxes.

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. ZF, which makes most of the product in Germany, has not yet OK’d it for off-road use.

So there are advantages and drawbacks to automatic and automated products. Get a lot of advice from actual users before you make a choice.