Test Drive: Paccar unveils 12-speed automated transmission

Jim Park

Paccar is the latest North American truck manufacturer to bring a proprietary automated transmission to market. Called the Paccar Automated Transmission, it’s a 12-speed, twin countershaft design that was conceived as an automated transmission, which is to say, it was designed that way. It’s not a manual box fitted with add-on shift-actuators. Paccar says it’s the lightest automated transmission currently in production. At just 657 pounds, it is nearly 200 pounds lighter than Eaton’s Advantage AMT.

The addition of the automated transmission completes Paccar’s goal of having a fully integrated proprietary powertrain. Paccar says its new transmission has been performance-optimized for MX-series engines and the new 40,000-pound drive axles unveiled in October 2016.     

“Last year’s launch of the Paccar axle was certainly a statement to our customers that we were moving toward our own integrated powertrain,” says Kenworth’s marketing director, Kurt Swihart. “We have spent a lot of time over the past few years working on proprietary calibrations for the transmission and the MX engines. The result is a deeply integrated powertrain that will deliver everything customers would expect from such a design.”

Swihart said during our pre-test drive briefing that the AMT take rate for the T680 has more than doubled since its introduction, going from 25-30% in 2012, to currently more than 70% of T680 on-highway builds. He calls that a rapid and dramatic change in customer preference, and he believes this new transmission will push the take rate even higher.

“We think moving from the Eaton Fuller Advantage series transmission to the Paccar Automated Transmission will be a game-changer,” he said.

The Eaton Cummins Automated Transmission Technologies joint venture is the technology partner on the Paccar Automated Transmission. “Eaton designed and will manufacture the transmission, but the calibrations and features are proprietary to Kenworth and Paccar,” Swihart says.

Production is set to begin in October of this year at Eaton’s San Luis Potosi Mexico facility.

Yes, Eaton’s Advantage 10-speed AMT will still be available from Paccar, as will the rest of Eaton’s manual and automated transmission lineup along with certain Allison automatics. Kenworth says it has no immediate plans to make the new automated transmission the standard offering.

Development of the Paccar Automated Transmission has been ongoing for the past three years. This includes design and testing ranging from standard line haul validation to summer and winter testing in extreme conditions. Swihart says when the transmission goes into production, it will be ready, willing and able to meet Kenworth’s linehaul customers’ needs and expectations.

“We benchmarked all the other great products out there and looked at what customers liked about those other offerings, and we found ways to incorporate and surpass the best design features that exist in the market today,” Swihart said during the briefing prior to our test drive. “Eaton, with its long history and expertise in transmission design and manufacturing, has hit a homerun with this product.”

Nuts, bolts and semiconductors

The transmission will hit the street geared with many features that Eaton customers are already familiar with, such as Urge to Move, Creep Mode, and Blended Pedal. These offer better low-speed maneuverability in low and reverse gears, while the latter allows the driver to “slip” the clutch by varying foot pressure on the brake pedal.

Also baked into the Paccar Automated Transmission are several drivability enhancements such as optimized gear selection, which select appropriate starting gears and make optimized shift decisions based on vehicle weight, engine torque, grade and throttle position. Even more fuel-saving features are offered as options.

“Kenworth offers Predictive Cruise Control as an optional feature today,” Swihart says. “If the customer specifies Predictive Cruise Control, then the GPS capability will integrate with the Paccar Automated Transmission. Also available is Predictive Neutral Coast, which uses GPS to shift into neutral earlier than the standard neutral coast.”

All the hardware is built into a lightweight all-aluminum enclosure, with an ECM that’s mounted externally. Wiring and sensors are enclosed within the case to protect them from the elements. The shifter mechanism was designed into the transmission rather than bolted on after the fact, and uses pneumatic actuators.    

Finally, the Paccar Automated Transmission is equipped with a 430-millimeter clutch with diaphragm springs and cushioned organic facings. These are said to provide more even pressure on the plates and smoother engagement. Clutch engagement is managed by an electro-pneumatic linear actuator, which Swihart says “provides a more robust and responsive way to actuate the clutch.”

The Urge to Move and Creep Mode features will amp up clutch stress over time, which seems to be why Paccar and Eaton have engineered what appears to be a very robust clutch and actuator system. From what we know now, there’s very little maintenance required on the transmission, and there are heat sensors on the clutch that will warn drivers to go easy on the thing before any damage occurs.

Driving experience

The next biggest question after who makes the transmission would be, how does it perform? I had about two hours in dense Seattle, Washington, traffic to find out — and even that short drive put the transmission through its paces. First of all, stop-and-go traffic means lots of shifting, and the hills and turns give the transmission lots of reason to be seriously engaged in the process. Running on a flat, open highway isn’t much of a workout for a gearbox.

My drive began with a few laps around the parking lot at Kenworth’s Research and Development Center in Renton, Washington, to observe the low-speed drivability. We were loaded to 72,000 pounds, enough to test the smoothness of the launch and few low-speed gear changes. I could feather the brake pedal at launch to make the truck creep back and forth very smoothly with no jerks or lurches. Even backing into a loading dock did not produce a cab-jarring torque surge as the truck smooched the dock pads.

Due to the transmission’s hard-wired determination to skip-shift whenever even remotely possible, some of the high-acceleration launches saw the engine revs getting close to 1,600 or 1,700 rpm coming out of second gear and heading for fourth. But on a gentle acceleration, I seldom saw 1,400 rpm when upshifting. Driving in stop-and-go traffic was pleasant and smooth, even starting on a hill. It seemed happy enough to deliver the acceleration when I put my foot right into it, but that’s so counterintuitive for so many reasons that I can’t see many drivers doing much of that. It was a little torquey at those times — so is any automated transmission — but this one seems less torquey than others I’ve driven.

Given the number of times it skip-shifted, they probably could have made it a six-speed rather than a 12. I don’t think I ever saw 3rd, 5th or 7th gear while accelerating up to speed. Once up to speed and cruising in the 70-95 kilometer per hour range, upshifts came at a comfortable and fuel efficient 1,400 or 1,500 rpm, usually dropping the Paccar MX-13 engine down to 1,100 — and on several occasions a sultry 1,000 rpm. The peak torque range on that engine extends from 1,000 up to about 1,400. That’s where all the pulling power is, and also where the least fuel is consumed. 

It’s pretty clear that the level of system integration between the engine and the transmission is pretty high.

Because of the traffic density, I reached top gear once. There, I cruised at 1,000 rpm at 95 kilometers per hour before having to exist the freeway. Much of the on-highway time was spent in 11th gear (direct) where cruise speeds were around 80 kilometers per hour and 1,200 rpm or so.

At various times the engine brake came on based on my cruise control settings, and did a good job of maintaining my set speed, plus or minus a few kilometers per hour for a more comfortable and fuel-efficient ride. On a few of the hills where I figured Neutral Coast might have kicked in, it did not. I guess the hills were a little steep for the transmission’s conservative sensibilities. Best to err on the side of caution, I suppose.

I got a good mix of city and highway driving in during those couple of hours, and the transmission handled it all with finesse and aplomb. It’s as smooth-shifting as any of the best automated transmissions on the market right now, and vastly better than some. Having 12 gears rather than 10 provides more gear selections for performance and fuel efficiency without the complexity of a multi-speed transmission, and the 17-inch clutch with its linear actuator (I still don’t quite understand how that works compared to a traditional actuator, but I’m learning) makes for a very smooth launch and stop.

Given that it’s a brand new product, albeit with three years of design, validation and durability testing behind it, some folks may be reluctant to dive right in, but my two-hour drive suggests there won’t be anyone holding out on the model because they don’t like the performance.   

The new Paccar Automated Transmission performs like a veteran and will surely meet the driver satisfaction test. They have backed it with an extraordinary five-year/1.2-million-kilometer warranty and with its oil drain interval also at 1.2 million kilometers, few fleets will find reasons to avoid it solely because of maintenance requirements. 

 

Unique features

Kenworth says several features make this transmission unlike any other currently on the market. It was something new for Eaton, which has traditionally eschewed the 12-speed configuration typical of many European designs. Still, Paccar is backing the transmission with a bold five-year/1.2-million kilometer warranty. Incidentally, the lube change interval on the transmission is also 1.2 million kilometers, which is well beyond most fleet’s trade-in interval. That means few first owners will ever have to drop the oil from the transmission.

The transmission uses a cooler-less precision lubrication system with an on-demand feature that gets lube oil where it’s needed, without wasting energy pumping it everywhere else. The fluid capacity of the system is 7.5 liters.

Gone from the dashboard is the transmission oil temperature gauge. It’s been replaced by a fluid pressure sensor that monitors lubricant level and pressure. If it senses a reduction in oil pressure, it will switch into a limp-home mode to prevent internal damage. A pop-up message alerts drivers to the low-pressure condition and urges them to pull over as soon as it’s safe to do so.

Based on its confidence in this system, Paccar is offering a “no burn-up” guarantee. “As long as the driver takes appropriate steps to prevent further damage, we will cover any potential burn-up that may result,” says Kenworth’s marketing director, Kurt Swihart. “That’s an industry first.”

The control module is mounted on the top of the transmission case, and has been designed with an internal, encapsulated wiring harness and internal sensors to help block moisture to protect the on-board electronics.

The shift actuators are electrically controlled and pneumatically driven, unlike the motor-driven actuators on many automated manual transmissions.

There’s is also a clutch protection system that monitors the temperature of the clutch. In high slippage situations, the driver may see a yellow or red pop-up warning, advising of a high-temperature condition. The driver would be advised to cease the current activity and allow the clutch plate to cool. This condition is unlikely to arise under normal conditions, but if the driver was slipping the clutch (in creep mode, for example), friction could cause the surface of the clutch plates to get quite hot. The warning will alert the driver before damage occurs. 

 

The driver interface

Frankly, I don’t know what else to call the driver interface. It’s no longer a gear shifter, and in fact, it’s not even a knob. It is, however, a nicely packaged control stalk mounted on the right side of the steering column. It’s big enough for even a huge hand, and it feels pretty solid. It’s very simple to use and offers six control functions on four separate axes.

The most obvious is the D-N-R selector. Twist it toward the dash into D and you go forward; flip it back into R and you go the other way. There’s a neutral position in between, which has an interlock with the parking brake. If the parking brakes are set with the shifter still in D or R, it automatically shifts the transmission into neutral, but the switch does not change position.

At the end of the shifter stock is the manual/automatic button. When it’s in automatic, the transmission does all the shifting. Pressing the button places it into manual mode from which the driver can control the shift by pulling the stalk back or pushing it forward. This is useful for maintaining a gear in a descent or when driving in stop-and-go traffic where the transmission might be constantly hunting for the right gear. Kenworth’s marketing director, Kurt Swihart, says this feature won’t be optional. The manual/auto button will be available on all orders. Some fleets would rather not have drivers mess around with gear choices.

An engine over-speed protection feature will upshift if necessary to protect the engine, even if the transmission is in manual mode. 

The stalk’s up and down axis is the control for the engine brake. Pushing the stalk fully up disables the engine brake. Down in the first position is the low setting, the second position is medium and the third position is the high setting. These positions are noted by a dash-panel icon showing an appropriate number of dots under an illustration of the engine. The fourth position is called “Max”, and the word Max replaces the three dots on the display. Pulling the stalk down fully into the Max position keeps the engine brake on the high setting while initiating a downshift to achieve maximum retarding power from the resulting higher engine speed.

I found it quite intuitive to use and never really had to think about what I was going to do before I grabbed for the stalk. That’s pretty good, considering I had only been driving the truck for a couple of hours.

 

Spec’s

Weight: 657 pounds

Gears: 12 forward, 2 reverse

Overall ratio: 18.85:1

1st gear: 14.43:1

11th gear: direct 1:1

12th gear: OD 0.77:1

Max horsepower input: 510 horsepower

Max torque input: 1,850 lb-ft

Max GCW: 110,000 lbs 

Warranty: 5 years/1.2 million kilometers

PTO: 8-bolt standard opening, bottom mount

Jim Park

Jim Park was a CDL driver and owner-operator from 1978 until 1998, when he began his second career as a trucking journalist. During that career transition, he hosted an overnight radio show on a Hamilton, Ontario radio station and later went on to anchor the trucking news in SiriusXM's Road Dog Trucking channel. Jim is a regular contributor to Today's Trucking and Trucknews.com, and produces Focus On and On the Spot test drive videos.

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