Allison’s 4000 Series is built for heavy-duty vehicles. - Photo: Allison Transmission

Allison’s 4000 Series is built for heavy-duty vehicles.

Photo: Allison Transmission

Work Truck sat down with Branden Harbin, executive director of Global Marketing for Allison Transmission, to learn a little more about the difference between an Automatic and Automated Manual transmission.

This is what we learned:

Work Truck: Can you briefly describe the differences between an automatic transmission and an automated manual transmission (AMT)?

BRANDEN HARBIN: The primary difference between a fully automatic transmission and an automated manual transmission (AMT) is the launch device. A fully automatic transmission employs a hydraulic torque converter coupling the engine to a planetary-geared transmission providing uninterrupted, continuous power shifts.

While the clutch pedal is removed in an automated manual, AMTs still use a standard manual gearbox with electrical or pneumatic clutch actuation, resulting in torque interrupts and loss of power during shifts. 

These power interrupts cost drivers time and lead to higher maintenance costs due to wear and tear on the clutch. By comparison, the automatic’s torque converter is not a wear component.

Beyond the uptime advantage of the fully automatic transmission, the torque converter provides improved maneuverability in soft/loose soil or where drivers need more control.

AMTs by comparison typically begin to overheat and will cut power to protect the transmission in soft/loose soil. A torque converter creates an infinitely variable gear ratio, allowing drivers to easily manage power to the wheels. Drivers can control vehicle speed to smoothly creep with precision, maneuver more easily and have more control on grades – all while protecting the driveline from shock and reducing vehicle wear and tear.

Without a torque converter, AMTs cannot deliver power to the wheels smoothly, creating more opportunities for inefficient and uncontrolled operation.

WT: What benefits does an automatic transmission have over an AMT on driver productivity?

HARBIN: Automatics provide multiple productivity advantages over competitive AMTs. Among the many advantages, automatics are more productive because they enable faster acceleration than AMTs.

Allison Transmission's torque converter smoothly multiplies engine torque at launch and keeps the transmission continuously connected to the engine's maximum available output during each shift, providing up to 14% faster acceleration. The full-power shifts provide superior vehicle acceleration, allowing more work to be done in less time.

By comparison, AMTs must cut engine torque at launch to protect the clutch. Therefore, AMT-equipped trucks never utilize full engine torque at launch. Unfortunately for those operating AMT-equipped trucks, this is when peak torque is most needed, to get a fully loaded vehicle moving from a stop.

AMTs do not benefit from engine torque multiplication because they require torque to be controlled or limited at launch to extend the life of the starting clutch. They also require a reduction of engine throttle at each shift, causing torque interrupts. These interrupts result in more shifts and lower vehicle speeds, requiring more time to do the same job.

As a second example, fully automatic transmissions eliminate the starting clutch, thereby eliminating truck downtime for required clutch replacements. This ensures maximum uptime and productivity for a fleet’s trucks. Many fleets have indicated they can operate a smaller fleet with automatic-equipped trucks, because each truck spends less time being repaired, whether proactively or worst case, reactively. In the case of a mixer truck, that lost downtime can be as much as $7,500 per truck per day.

And, that’s assuming that the barrel wasn’t full when the AMT clutch failure occurred, which would add additional repair cost to replace the barrel.

WT: What benefits does an automatic transmission have over a fully manual transmission on driver productivity?

HARBIN: An automatic has the same benefits over manual transmissions in terms of uninterrupted power at every shift, without the physical toll on a driver who has to shift all day or the wear and tear on the manual clutch.

With reduced driver fatigue, automatics increase driver retention and provide a more controllable environment for the driver and vehicle.

Smooth, seamless operation allows the driver to easily maneuver the vehicle so attention can be focused on the job at hand.  It is also easier to recruit drivers to operate an automatic compared to increased training to drive a manual transmission. Fewer drivers are available today who have experience driving a manual transmission.

Many drivers have indicated that their careers have been extended by transitioning from a manual to a fully automatic transmission.

While beneficial for the individual, this has an added benefit of addressing the driver shortage problem our industry is facing as well.

And, the added cost of the automatic transmission is often significantly less than the cost to the business to recruit, train, and retain a replacement driver.

Vehicles with a manual transmission also have reduced maneuverability, difficulty on narrow roads, soft soil, steep grades, or backing into loading docks. Additionally, power take-off (PTO) cannot be applied on the fly as it can be with an Allison automatic transmission.

All of this can lead to driver frustration, abuse of the driveline components and reduced productivity.

WT: Are there any benefits/pros that a manual or AMT does still have over the automatic transmission?

HARBIN: In the short term, manuals and some AMTs cost less than a fully automatic transmission, from an acquisition price perspective. However, due to clutch maintenance and vehicle downtime of manuals and AMTs, vehicles equipped with an Allison Automatic tend to have lower maintenance costs, higher resale values and a lower total cost of ownership over the life of the vehicle. 

There is no clutch to wear out on an Allison, and reduced maintenance intervals keep the vehicle on the road longer.

This is why most large national work truck fleets leverage Allison automatics. They have realized the superior total cost of ownership advantages Allison Automatics provide.

While the manual clutch pedal is removed on an AMT, the mechanical clutch still facilitates the vehicle’s launch and will wear and eventually burn out, requiring traditional maintenance and replacement.

Additional wearable clutch components include:

  • Clutch Cover/Intermediate Plate
  • Clutch Disc Assembly
  • Adjusting Mechanism
  • Clutch Brakes
  • Solo Clutch
  • Cross Shaft
  • Pilot Bearing
  • Input Shaft

Over time, manufacturers of AMTs have attempted to mimic the inherent capabilities of an Allison Automatic by promoting features such as Urge to Move, Creep Mode, Power Launch, Rock Free, Hill Assist, and Blended Pedal. However, all of these features can add cost and come at the expense of clutch wear and driveline failures.

And when push comes to shove, AMTs will always behave in a manner that protects the starting clutch. When a driver needs it most, the AMT will likely cut torque and limit driver input in an effort to protect the automated transmission.

WT: Anything else you would like to share today?

HARBIN: There is some misinformation regarding fuel efficiency of an automatic transmission versus manuals or AMTs.  Some people believe the driver of a manual has better control over fuel efficiency, which is not true.

Fully automatic transmissions have been enhanced with new technologies to improve fuel efficiency including neutral at stop, acceleration rate management and dynamic shifting.

In nearly every application, particularly for work trucks, an Allison Automatic can achieve equivalent or superior fuel economy to manual and automated manual transmissions.