Perhaps the most crucial part of a semi-truck is its transmission. While manual transmissions are much more prevalent in semi-trucks than in cars, there’s still a movement toward automatic transmissions on the rise.
Is there a clear-cut answer when it comes to automatic versus manual transmissions for semi-trucks? The answer is in how you look at it, but there are clear arguments for both sides of the gear.
What’s the Difference?
The basic difference between a manual and automatic transmission are the ways that the cars shift gears.
When you’re using a manual transmission, you’re the one who is telling the vehicle when to switch gears. You use a clutch and the gas pedals to signal when it’s time to shift upward or downward. An automatic transmission does this process for you, usually using a computer to detect when the changes need to be made.
Automatic Transmission for Semi-Trucks
In the early stages of technology for automatic transmissions for semi-trucks, the technology was having trouble adapting. The computers or hydraulic systems hadn’t had time to catch up with what drivers wanted, or weren’t able to figure it out.
Drivers complained about transmissions struggling when on inclines or declines, or transmissions sticking in gear when they weren’t supposed to. It’s partially because of this that many older semi-truck drivers still favor manual transmission.
However, technology has adapted. Now performance is smooth and almost undetectable. Rarely will a driver run into issues with the shifting mechanisms on their automatic transmissions. These vehicles are two-pedal designs and considered much easier to manage than manual transmissions, making them preferred by the younger generation.
Automatic transmissions benefit from greater efficiency on many levels. Brad Williamson works at Daimler Truck North America as the powertrain marketing manager. He speaks to the updates that automatic transmissions offer, and how he thinks that a driver really can’t match the automatic transmission’s power.
“Information is key. If you designed both the engine and the transmission, then they can ‘talk’ to one another and share critical information, like what the driver wants, the fuel map, the load, the grade and what the engine is trying to do,” he says. “The transmission can manage all this information and deliver the best performance possible given all those criteria.
A driver just can’t do that consistently. Even if they had all that information, they couldn’t process it and manage the shifts to deliver the same level of performance an automatic transmission can.”
Semi-trucking is seeing advances even still with that performance. Complete powertrain integration is going to be coming to automatic transmissions, which means that that information he mentioned is going to be shared in order to get the best fuel economy possible, at every single point of the drive.
The director of powertrain sales for Mack Truck is excited about this technology. “It all boils down to the electronics,” says David McKenna. “When you have Vendor A supplying an engine and Vendor B supplying a transmission, rarely do those two components share 100 percent of their information 100 percent of the time.
Typically, the transmission in those instances ends up making decisions with about 75 percent of the data it needs to make an optimal shift.” With new advances in technology, this conversion is going to drive into the 80 and 90 percent.
At the same time, because an automatic transmission has more electronics and working parts, it can be more expensive to fix. Automatic transmissions are also more expensive to buy than manual transmissions, potentially ranging to a few thousand dollars in difference.
Automatic transmissions are on the rise, and their technology continues to improve. As time goes on, and more advances are made, trucking is likely going to go fully automatic.
Manual Transmissions for Semi-Trucks
Manual transmissions put trucking into the hands of the drivers.
“There are still a lot of highly experienced drivers out there who can get the most out of a manual transmission,” says Shane Groner, the manager of NAFTA product development at Eaton, a large trucking supply company. “Those gearboxes are essentially bulletproof. If you’re a fleet and you’re blessed with an abundance of experienced drivers, and upfront costs are still your primary expense driver, then it’s hard to argue with manual transmissions.”
He goes on to speak about the different skill sets of newer drivers entering the trucking field. “Many young drivers have never driven even a car with a manual transmission, so they lack even basic familiarity with them. The driver demographic is changing. Older drivers are retiring, and they are not being replaced.”
Because a person is in control of the transmission instead of a machine, the overall performance is generally lower for the drive all around. This is a huge concern for fleet owners who are having their costs cut into because of wasted fuel.
Having to shift a manual transmission is also thought to contribute to the stress of truck drivers. Because it requires a fair amount of concentration, it can strain the driver and make their job more difficult.
The Third Type of Transmission
If you thought that you were just looking at automatic and manual transmissions, you were only half right. There’s a combo of the two out there called an automatic manual transmission, or an AMT.
AMTs sometimes mistakenly get referred to as simply an automatic transmission, because they essentially appear as one. It’s a combo of an automatic and manual transmission because it’s a mechanical transmission that uses automation through computers, actuators, and sensors that help to shift the fork and the clutch. What this means is that a computer control system shifts the manual transition’s gearbox.
If you want the best of both worlds, talk to your supplier about getting an AMT for your truck.
Where is the Industry Headed?
Many people in the industry consider manual transmissions to be outdated technology. Those who have been lifelong drivers are very used to manual transmissions and have shifted gears for decades. However, manual transmissions seem to be on the downtrend as far as new trucks go.
This is due to several of the previously discussed factors, but mainly because automatic transmissions are viewed as more efficient, and tend to be easier to learn. In a time where there’s a shortage of drivers, the industry can’t afford to train a generation of drivers who didn’t grow up driving a stick-shift. They need to put people in trucks quickly, and automatic transmissions help speed up that process.
President of Heavy Metal Truck Training Gary Pressley says that “[i]n the next three to five years, pretty much everything is going to be automatic.”
As mentioned, it’s also a matter of fuel efficiency. Drivers with years of experience might be able to maneuver their manual transmissions into getting fuel efficiency that just about matches an automatic transmission, but not many drivers can.
Automatic transmissions will look at factors such as engine speed, engine torque, vehicle angle, and vehicle speed before shifting. Newer drivers just don’t have the experience to evaluate all those factors, especially if they never drove a 4-wheeler in manual before.
Other drivers say that having a manual transmission helps keep them alert because it gives them more of a task to do. When you’re not thinking about shifting gears, you’re letting yourself relax more, which could lead to drowsiness. Still, others tout that an automatic transmission is safer because there’s less to think about and distract someone on the road.
In all, the industry is shifting toward automatic transmissions, but there’s still quite a following of diehard manual transmission enthusiasts who remain convinced it’s a better option.
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