Leg rest

The electronic revolution has brought an amazing innovation to trucking: inexpensive, self-shifting transmissions. These units use a microprocessor and tiny electric motors or electrically activated pneumatic cylinders to manage the shifting.

Most are three-pedal designs – clutch, brake and accelerator – and coordinate engine and transmission input shaft rpm and float shift just as skillful drivers do, once the driver has used the clutch to start the vehicle moving. More recently, two-pedal designs, which operate the clutch for the driver, have found a place in the market.

Two major factors have made this technology welcome. Urban congestion has reduced traffic to a crawl on some interstates, making shifting and clutching a much greater challenge. Secondly, a driver shortage has brought in many inexperienced operators, most of them nurtured on automatic car transmissions and many carrying no emotional baggage about having to shift to be a real truck driver.

Automatics offer improvements in safety, productivity and comfort. For this, of course, you pay – and prices vary considerably. Whether the improvement is worth the cost depends on what you buy, which benefits are important to you and how the vehicle is used – where it runs and what the traffic is like.

“What I am looking for is improved safety and reduced maintenance,” says Mike Mount, whose 50-vehicle Mount Trucking is headquartered in Columbus, Ind. “If you take shifting away from the drivers, it saves the driveline, too. We have some Eaton AutoShifts with 800,000 miles on them, and those trucks have required very few repairs.”

Mount has purchased two ZF Meritor FreedomLine transmissions in Peterbilt 387s. “We decided to try some fully automatic transmissions because we have a number of husband-and-wife teams and many inexperienced drivers,” he says. “Our trucks run from here to the West Coast. On the L.A. freeways, you have to sit there and hold the clutch down because the traffic just keeps inching forward.”

The FreedomLine “is extremely quiet, and it shifts nice,” Mount says. “We have some drivers with 30 years on the road, and even they say they’d like to have one after trying them out.”

The list price for an Eaton Fuller AutoShift 10-speed is $4,000 to $4,500 on a Volvo VN. The 18-speed version is $6,000. The FreedomLine costs about $1,000 more than a compatible AutoShift, says ZF Meritor’s Charlie Allen, director of sales and marketing. Allisons may list for as much as $15,000 on the option sheet, though $10,000 is much more realistic, given the usual reductions from list prices. Owner-operator Fred Lapp got one in his Freightliner Business Class vehicle several years ago for less than $7,000. Nick Bond, vice president and general manager of Russ Moore Transmissions of Fort Wayne, Ind., says a Class 6 or 7 truck can be converted to use a remanufactured Allison with a substantial warranty for about $5,500.

Whatever the price, safety is the benefit that is most commonly mentioned. Brian Coe, business development manager for AutoShift systems at Eaton Fuller, says fleets “find that their accident rates improve – especially the little fender benders. These often happen as a vehicle merges into traffic. The operator has so much on his mind. You take the worry of ‘Is the engine at the right rpm?’ out of his job so he can concentrate on looking in the mirrors and steering, and it can be a big plus.”

Fuel savings, Coe says, depend on the driver. “The best driver in the world doesn’t need it. But it brings the less-skilled driver up to a higher level.” An automated transmission shifts up every time you throttle back to cruise, even when a downshift may be needed soon. It also downshifts whenever the engine gets well below the torque peak and the driver hits the throttle. Pampering the diesel like this makes it more efficient. Allen says this may be good for fuel savings of 3 percent to 5 percent, for instance from 6 miles per gallon to 6.2 or 6.3. That fractional increase adds up to big money.

Automatics reduce drivetrain wear, too. Even the three-pedal units float shift between gears, which saves clutch wear if drivers use the clutch when shifting. Power is always re-applied smoothly after a shift, minimizing shock loading. The clutch collars are never abused because the processor knows the exact rpm of engine and output shaft and matches them perfectly.

Most automated transmissions use components originally designed to be operated by the driver that could not work by themselves before microprocessors existed. Automatics are transmissions designed to be self-shifting and that don’t require the driver to clutch. With automated and automatic designs (except the SureShift), the transmission always chooses the right starting gear, cutting clutch wear.

The Eaton Autoshift 7-speed is an automated, medium-truck transmission based on standard hardware, but with the synchronizers removed because the computer float shifts.

All the two-pedal units have self-adjusting clutches, and the FreedomLine warns you if the clutch gets out of adjustment. Dale Wilson, product engineer for Transmission Technology Corp., says, “The engine and driveline speeds are synchronized after a shift, so there’s no large adjustment of engine speed at the expense of the clutch. There’s also no lurch with the accompanying driveline shock.” Starting in the right gear with minimum throttle and smooth clutching will do more to minimize clutch wear and driveline shock. Eaton Fuller engineers believe the clutch in the Fuller Automatic 6-speed, which runs in filtered fluid, will give much longer service life than a dry clutch, especially in city pickup and delivery service.

Chuck Venis, manager of strategic marketing at Allison, says the best applications for Allisons are refuse trucks, discharge mixers and dump trucks. Heavy equipment haulers also use them because manual shifting is difficult with such loads.

Mack’s vocational product manager, Steve Ginter, says the company has worked with Allison. “Together we have made significant inroads into the refuse industry,” he says. Mack makes a version of its E-7 engine governed at 1,950 rpm rather than 1,800 to work with the Allison. Although the upcharge is “substantial, a decision to go with an Allison comes with the expectation that the fleet will be experiencing no clutch wear and generally less drivetrain maintenance,” Ginter says. This makes it ideal in many construction applications. The unit’s performance in low-speed acceleration and hill climbing can increase trips per day significantly. The only maintenance normally required, Venis says, is fluid and filter changes – the unit self-compensates for clutch wear. The use of synthetics can extend fluid changes to 100,000 miles, with filters at 50,000.

Owner-operator Lapp reports that he put 370,000 miles on an Allison in an earlier vehicle with minimal maintenance, using fluid analysis to extend changes. He recently purchased a Freightliner FL112 and switched to a 10-speed AutoShift because having more gears allowed better fuel economy at cruise. But he loved “the reduced driver wear and tear” of clutchless driving and will look for a two-pedal transmission next time.

Choosing whether to purchase one of these gearboxes requires careful cost analysis and a review of your operating conditions and driver skills. If you’re an excellent driver running coast to coast between warehouses located far from cities, you probably have little use for an automatic unless you experience fatigue or are willing to spend the dollars just to drive with less effort. If you’re a less-skilled driver running in a city, and you have maintenance and safety concerns, the unit could well help you control your costs.


The torque converter on the front of this Allison allows you to start fully loaded, on a steep upgrade, with no clutch wear.

Automation sensations

Several automatics are on the market, and they differ in several ways. They’re listed here from simplest to most complex.

ZF MERITOR SURESHIFT

Charlie Allen, director of sales and marketing for ZF Meritor, says the company’s SureShift “gives the maximum bang for the buck.” It uses a simple “driver interface” lever. After selecting the forward direction and pushing in the clutch, the driver starts in the ordinary manner using the accelerator and clutch. Then the lever is pushed forward to upshift, backward to downshift.

This unit float shifts the conventional ArvinMeritor constant-mesh 9- or 10-speed transmission. It breaks torque using the two processors, brings the engine to synchronous rpm (matching engine and transmission speeds for the next gear with speed sensors) and then actuates the shifting forks with air-actuated cylinders. Those cylinders are turned on and off by solenoids operated by the unit’s processor.

Finally, power is reapplied smoothly via the two processors. The driver can easily signal the unit (via a button on the joystick) to skip one or two gears. Although the driver must make all shift decisions, the unit denies the driver’s request if it will over-rev or lug the engine down too much.

The unit must be specified with an engine brake, is intelligent enough to know the truck is on an upgrade and will engage the engine brake to make difficult upshifts.

EATON FULLER AUTOSHIFT

The AutoShift electronics and electric motor-powered shift actuators shift the standard Eaton Fuller transmission and control the engine throttling via the transmission and engine processors. The driver uses the clutch and throttle to start in the ordinary way, after putting the unit in drive and depressing the clutch. AutoShift then makes all shift decisions, depending on grade and throttle position.

It breaks torque and float shifts, re-applying power smoothly as it shifts. The unit is smart enough to automatically engage the engine brake to speed upshifts on upgrades. (Specifying the unit requires an engine brake, too.)

If the driver wants control of shifting, he can shift the selector to hold to keep it in the present gear. He can then push one button to upshift and another to downshift. The unit will refuse to shift when outside the proper rpm range.

The unit normally starts in second gear, which is just right under most conditions with the 10-speed version. The driver can easily use the hold feature to start the unit in first, third, fourth or fifth.

The AutoShift also comes with 18-speed transmissions for owner-operators and heavy fleets, 6- and 7-speeds for medium trucks. The 18-speed AutoShift is so intelligent it can skip gears and splits as appropriate, depending on throttle position and grade.

EATON FULLER AUTOMATIC

6-Speed

This two-pedal unit, designed for medium-duty trucks, combines a 6-speed transmission with quiet helical gearing and a multi-disc wet clutch. The transmission’s synchronizers are removed. An inertia brake is added for upshifts on upgrades, because the engines used in these trucks don’t have internal brakes. The transmission uses synthetic fluid, but the wet clutch unit uses automatic transmission fluid, with its own pump and clutch hydraulic actuator piston linked to the microprocessor electrically.

When you select Drive, the hydraulically actuated clutch engages just enough to give that gentle push (what Eaton Fuller calls the “urge to move”) that is typical of torque converter automatics, to make starts smoother. The processor engages the clutch smoothly when you hit the throttle, and then the transmission begins going through the gears, float shifting like its simpler brothers. On an upgrade, the inertia brake slows engine and gearing together for quick upshifts.

The unit drives as easily as a fully automatic.

TTC’S AMT-7

Transmission Technology Corp. will soon introduce a two-pedal, fully automatic 7-speed medium-duty transmission, the AMT-7. It uses a single-plate dry clutch and synchronized transmission with quiet helical gears.

The clutch operation and gear shifting are all electronically controlled and hydraulically activated using a hydraulic pump and accumulator, so the pump runs only part of the time. The hydraulics use ATF in a separate reservoir. The microprocessor is mounted on the side of the transmission, and the hydraulics and solenoids are inside the bell housing, so there are no hoses or pipes.

As with the other two-pedal designs, the position of the clutch is fed back to the microprocessor so it can release it smoothly, as an experienced driver would. The clutch gently begins to engage as soon as the driver releases the brake, which allows the skillful driver to gently move the brake pedal up and down and coax the truck forward or backward an inch at a time without touching the throttle. Since the transmission is synchronized, it declutches and shifts in the ordinary way, with no double-clutching or float-shifting.

ZF MERITOR FREEDOMLINE

The FreedomLine is a premium 12- or 18-speed two-pedal automatic. The transmission is a simple, twin-countershaft, constant-mesh design with all-helical gearing for quiet operation – a rarity in heavy trucks. Its case is aluminum, to keep weight down. This was the first two-pedal design using relatively standard components.

The FreedomLine has an integral single-plate clutch that’s operated via an electronically controlled, air-powered piston. It declutches and uses the integral inertia brake to make fast upshifts, says ZF Meritor’s Allen.

The unit’s microprocessor is integral and mounted inside the transmission case, minimizing the number of connectors. Operation is extremely smooth and quiet. Load sensing allows it to do a very skillful job of adapting and skipping full gears or splits when the load and shift points permit. It drives like the most skillful driver, even as an 18-speed. But the driver can take control and operate it just like SureShift.

THE ALLISON AUTOMATIC

In Allison transmissions, the torque converter replaces the clutch with a hydraulic turbine drive. The converter lets the vehicle start out with no mechanical slippage, just the flow of oil. It multiplies torque about 21/2 times at the beginning, then gradually locks up as the speed increases. Allisons have five or six gear ratios provided by planetary gears, multiple-disc wet clutches, and hydraulic pistons. The unit uses the torque converter in the first two gears, locking up completely like a manual at the top of second. All shifts occur under full power. The latest World Transmissions use an electronic processor.

The Allison is complex and expensive but overcomes a multitude of clutch and driveline maintenance troubles in applications with frequent, hard starts and difficult upshifts. Acceleration from zero to 25 mph using the torque converter is nearly twice as fast as with automated mechanical transmissions.

Showcase your workhorse
Add a photo of your rig to our Reader Rigs collection to share it with your peers and the world. Tell us the story behind the truck and your business to help build its story.
Submit Your Rig
Reader Rig Submission