Drivers will be happy with the X15/Endurant powertrain in 2018 trim.
 - Photo: Jim Park

Drivers will be happy with the X15/Endurant powertrain in 2018 trim.

Photo: Jim Park

Cummins and Eaton have been holding hands on component integration for years. In 2013 they announced an engagement of sorts with the launch of the SmartAdvantage powertrain. Last year, with the new Endurant transmission launched through the Eaton Cummins Automated Transmission Technologies joint venture, the last two independent major component suppliers have figuratively tied the knot.

Before the end of this year we will see a new suite of performance features for the X15/Endurant powertrain that take engine/transmission integration to its highest level ever. In my opinion, this pairing is as tight as any of the vertically integrated OEMs’ powertrains. 

Last summer, I went to the Cummins plant in Jamestown, New York, to hitch a ride on a Kenworth T680 equipped with the new powertrain. At that time, some of the calibrations were still in development and not all the features had been named, so I couldn’t very well write about them in a test drive story. You’ll soon be hearing officially about what the engineers have been up to. In the meantime, I can tell you it will be worth the wait.

The Endurant was introduced to the market in September 2017 as a completely new, clean-sheet design conceived from the beginning as an automated transmission, not as a manual with add-on shift actuators. It’s a 12-speed, twin-countershaft design weighing just 657 pounds. Direct drive is in 11th gear, with 12th gear offering a 0.77:1 overdrive.

Our test drive took us along I-86 between Jamestown and Erie, Pennsylvania. That stretch has loads of rolling hills and a couple of climbs long and steep enough to prompt a downshift or two in some cases. The engine model was an Efficiency Series X15 450 SA, 450 hp with 1,550/1,850 lbs-ft. of torque @ 1000-1400 rpm. It also had the full ADEPT feature suite, including SmartTorque 2, SmartCoast, and Predictive Cruise Control. Overall, a pretty typical fleet spec powering a pretty typical 65,000-pound-gross-vehicle-weight load.

As innovative as it is, Endurant is still just a box full of gears until it’s programmed and bolted to a Cummins engine. I’ll get to the latest feature updates shortly, but first, here are my basic driving impressions of the X15/Endurant powertrain.

The Endurant is a completely new, clean-sheet design conceived as an automated transmission. It’s a 12-speed, twin-countershaft design weighing just 657 pounds. Direct drive is in 11th gear, with 12th gear offering a 0.77:1 overdrive.
 - Photo: Eaton Cummins Automated Transmisison Technologies

The Endurant is a completely new, clean-sheet design conceived as an automated transmission. It’s a 12-speed, twin-countershaft design weighing just 657 pounds. Direct drive is in 11th gear, with 12th gear offering a 0.77:1 overdrive.

Photo: Eaton Cummins Automated Transmisison Technologies

Behind the wheel

If previous generations of Eaton automated transmissions left a bad taste in some mouths, the Endurant is like a bottle of mouthwash. The closer ratios between the 12 gears allow for more skip-shifting opportunities and much smoother shifts to boot. It launches very smoothly, whether the driver is kind to the throttle pedal or just stomps on it. The level of acceleration changes with the “aggressiveness” of the throttle application, but it’s all carefully managed to not push the engine out of its optimum operating range. The new calibrations favor using as few gears as possible while accelerating, based on weight and grade, and are actually more inclined to skip up through the gears if the driver is firmer on the pedal.

My first few runs through the gears were fairly gentle, in keeping with my driving style. I think I skipped two gears on the way from 2nd to 12th. My guide and instructor, Mike Hicks, a vehicle systems integration/calibration engineer at Eaton Cummins Automated Transmission Technologies, suggested I try driving it the way most drivers would, and sure enough, all the odd-numbered gears seemed to disappear. On one launch from a stop sign, I floored the pedal and we hit 6th gear on the second shift and then went right to 8th. I went from 2nd to 8th in two shifts and the engine revs never got carried away.

I hate to admit it, but I think my driving style has gone out of fashion. The team that put this calibration together recognized that many of today’s entry-level and junior drivers are going to drive this truck the way they drive their cars, and they have wisely tuned the calibration to that driving style. It responds really well to a more aggressive throttle application, and when cruise control is set it settles into a more “seasoned” driving style basically invisible to the driver.

Cummins’ X15 for 2018 offers several calibration updates that improve driveability and performance when paired with an Endurant transmission. 
 - Photo: Jim Park

Cummins’ X15 for 2018 offers several calibration updates that improve driveability and performance when paired with an Endurant transmission. 

Photo: Jim Park

New features

The quick-shifting, fast-accelerating performance is new to the product, thanks to two new features. The first, called Engine Assisted Shifting, uses the turbocharger as an exhaust brake of sorts to slow the engine down with exhaust backpressure for faster upshifts. That process also preserves boost pressure so there’s no lag time while the turbo spools up again after the shift. This helps drivers get up to speed faster without driving more aggressively. 

On top of EAS, Performance Shift Optimization allows for higher engine revs in 4th gear and up, encouraging skip-shifting and thus getting the truck up to speed faster with no fuel consumption penalty. The fuel savings comes from fewer gear changes through the lower, less efficient ratios. 

Because Hicks had his computer connected to the engine, he was able to turn these features on and off for demonstration purposes. The difference was quite obvious.

I noticed another of the new features almost immediately, even though I wasn’t consciously aware of it initially. Launch Control Tuning all but eliminates the lag time as the clutch engages at launch. The truck literally starts moving the moment you depress the accelerator pedal. This is sure to be a hit with drivers.

The above-mentioned features are standard with the latest calibration and software update, which is backward compatible with the first models released earlier this year.

I also tried out two optional features that expand on technologies now available in the ADEPT suite: Accelerator Coasting Management and Predictive Gear Shifting.

ACM allows the transmission to coast in neutral on slight downhill grades even when the cruise control is not engaged. Protections are baked in to prevent the truck from going above a customer-selected speed, whereupon the transmission re-engages and the engine brakes activate. Coasting takes advantage of vehicle momentum without the parasitic losses from engine friction.

Predictive Gear Shifting uses look-ahead data from the Predictive Cruise Controls’ GPS and terrain maps to pick the right gear for an upcoming hill. It reads engine load, vehicle weight, and grade inclination to match engine output with the right gear to reduce or eliminate downshifts while climbing. This one confused me a little, as it caused the truck to perform in ways I wasn’t expecting, like downshifting early – or at least what I would call early. We did in fact climb the grade without shifting on the hill; we just shifted before we got to the hill.

As I mentioned earlier, my driving style was somewhat at odds with this setup. Once I accepted the fact that it was calibrated for a different driving style, it all made much more sense. The Eaton-Cummins JV will sell thousands of these engines to fleets with legions of exactly the type of driver that will like this calibration.

However, drivers like me can still order a calibration that will suit their driving style, too. That’s the nice thing about electronic controls – you can take the same pile of hardware and make it perform exactly for its intended market.

Basically, this powertrain will appeal to everyone who likes red engines, because you can get it the way you want it.

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