Over the years, engineers at Eaton have been refining their automated mechanical transmissions (AMTs). In that time, I’ve driven and judged them from a driver’s perspective, and praised and criticized them in my writings. This goes back to about 1990, when the company field-tested its CEEMAT hydraulically controlled gearbox that didn’t quite work out. It took electronic controls—microcomputers, really—to bring the potential for preciseness and smoothness to the concept.
The potential was there but the execution lacked the finesse shown in competitor products that appeared along the way. To be sure, clutch engagement was smooth and gear changing usually was correct, if not always as exact as it should’ve been. But my main gripe was that Eaton AMTs let engines rev out almost to their redlines, which violated the principle of progressive shifting taught to me by wise old hands many years ago. Engineers have corrected that, as we’ll see in this jaunt on and off the track at Eaton’s proving grounds near Marshall, Mich.
First, what’s progressive shifting? It’s upshifting at low rpm at low road speeds, then revving the engine higher as speed increases. This makes sense because torque, not horsepower, is enough to propel the truck as it’s moving slowly. Speed requires horsepower, so higher revs, where horsepower is made, are OK at higher road speeds. That’s the theory I learned back in 1975, when I first learned to drive 10- and 13-speed manual transmissions.
There are exceptions for dumpers, mixers and other vocational trucks that travel off road. Uneven terrain will have a truck speeding up and slowing down, and it’s impractical to constantly up- and downshift to keep revs in a proper range. Climbing steep grades can also require higher revs, for performance also requires horsepower—something just as true out on the highway. And, if a driver wants to upshift while climbing, he needs to rev the engine to its redline and build some momentum, which gives him time to grab the next gear. He might have to use the clutch brake, if the truck has one, to slow down the transmission’s input shaft so he can slide the next gear into place.
That last example is only partly true, because our driver might find that he can upshift faster at lower engine revs—another argument for progressive shifting. Also, modern engines now make both healthy horsepower and hefty torque at low revs. Peak torque now typically comes at 1,000 rpm and less, and maximum horsepower is there at 1,600 or so. Upshifting early makes more and more sense. And that’s why I was perplexed when Eaton UltraShift transmissions didn’t do it, and irked when engineers resisted my arguments.
But that’s changed. The latest products, called UltraShift Plus, can be programmed for specific applications and preferences, which engineering manager Ben Karrer explained by phone last spring and again recently. Meanwhile, marketing and p.r. people—probably tired of hearing me complain—invited me to their proving grounds to see how the programming has affected transmission operation. Karrer was among the folks present, and we covered a lot of ground in a few hours.
Two tractor-trailer rigs were ready for driving, and I eagerly took them out onto the long, oval track. One was an International LoneStar sleeper-cab road tractor with a 475-horsepower MaxxForce 13 and a 10-speed LAS (linehaul active shifting), and the other was a Peterbilt 367 daycab tractor with a 13-speed MHP (multipurpose high-performance). A third platform, called MXP (multipurpose extreme performance), includes 18-speed gearboxes with higher torque capacities usable for heavy hauling on and off-road. For this article, I concentrated on the Pete 367 because it’s a vocational model. Its MHP was mated to a 600-horsepower Cummins ISX15, so “performance” pertained to engine and tranny both.
Right off the line I could tell that upshifts came sooner than I had experienced with past UltraShifts. Instead of revving to 1,900 and more, the engine revved to about 1,500 before the transmission went to the next gear while in Low range, and to 1,700 or so in High range. That was better, but not low enough, I told Karrer, who was along for the ride. No problem. He had his laptop plugged into the data-bus port under the dash and began e-talking to the tranny’s controls. He reprogrammed them so upshifts came a couple of hundred rpm lower, which I liked.
“Shift points are one of the features available with UltraShift Plus programming,” he explained. “The set points govern the behavior of the transmission. It’s higher rpm for vocational, and lower for highway. There are roughly 20 shift-point calibrations.” They can be done with all models, from 8-speed Low-Low vocational gearboxes to the 18-speed extreme-performance transmissions.
“Some shift points are set for specific engines, like the Cummins ISX15-One family, which goes up to 450 horsepower,” he said. “This is for linehaul, and our settings are optimized for fuel economy based on that engine’s fuel map.” The 600-horsepower version I drove was a standard heavy-haul engine, whose transmission shifts at higher engine rpm than a linehaul. Performance engines can be set to shift from 1,900 down to “low-rpm progressive,” one of the shift-point calibrations. It’s driver and owner influenced, so can be modified, as he did with his laptop after my comments that shift points were still a little high.
An owner or driver cannot usually reset those shift points, Karrer said, because it requires ServiceRanger, an Eaton program that’s used at truck factories and dealers to set parameters per order specifications. A fleet might buy the program if it services its own trucks.
That brings up a point: If you’re ordering an UltraShift Plus on your next new truck or tractor, or buying a used truck with an UltraShift, know how you want it to behave so you can specify the settings right at the factory. Then upon delivery, load the vehicle and take it for a drive. If it doesn’t shift like you want, tell the dealer to reset it. You might have to spend time on the phone or even stand with the technician as he does the reprogramming, but it’ll be worth it because its operation will be pleasing and, if you choose progressive settings, it’ll save you money in fuel.
Of course, a driver who prefers lower rpm can get them with a light foot. In that Peterbilt, revs stayed reasonable if I eased into the accelerator, even before Karrer reset the shift points. Even then, when I stomped on the pedal, revs went higher to gain the performance I wanted. Drivers can also use the Manual controls on the UltraShift Plus’s selector to effect shifts. Recently, I did that in a Peterbilt 579 highway tractor whose engine revved several hundred rpm more than I thought necessary. I punched the Manual button, then touched the Up switch to make most gear changes. This shouldn’t be necessary with an automated transmission, but can be done until it’s reprogrammed.
Conversely, a driver can hold each gear longer to gain some acceleration or some engine braking on long downhill stretches, and that makes a lot of sense. He can also keep revs high just because he likes it, which makes no sense at all. Some fleets spec a selector without the Manual function, which I think is short-sighted because with a little training a driver can use it to advantage. For his edification, an LED readout on the instrument panel tells which gear the tranny is in. On the automated products, each gear is numbered starting with 1 for low and 10, 11, 13 or 18 for top gear. The start-up gear is also programmable, and for a 13-speed would usually be 2nd or 3rd with the driver able to select a lower gear for starting on a steep grade.
But simply put in D and driven, UltraShift Pluses usually do well on their own. The two I drove that day on the track and on other occasions all shifted smoothly and with no clunking. It wasn’t this way with the early AutoShifts and UltraShifts, and I applaud the progress. Then there’s clutch operation: AutoShifts had manual clutches with a pedal, so it was up to the driver to stop and start correctly. UltraShifts and the later Plus models all have automated clutches, which seem to work well.
On this day, I took both trucks onto a steep test hill to check out clutch operation and found it impeccable: smooth engagement with no vibration or bucking of the chassis, even on a 15-percent portion, and much smoother than I could’ve done with a manual. The Pluses also have a hill-holding feature that, working with the truck’s anti-lock braking system, keeps the brakes set for three seconds after the driver takes his foot off the pedal, then releases them. By this time he should have begun pressing the accelerator, and the clutch will engage and the truck will begin to move up the grade. Competitors also use the three-second timing, but I think the brakes should just stay on until the driver presses the accelerator. I’d ask Ben Karrer to program that into the tranny’s e-brains if I were buying an UltraShift Plus.
And I almost certainly would buy it if it were available, and I wouldn’t sweat the price because they’ve come way down since the old days, when Eaton tried to sell it against Allison’s full automatics with similar stiff upcharges. Prices are set by the truck builders, of course, but Eaton marketers say that $4,500 to $6,500 over a comparable manual transmission are typical premiums, which I believe are reasonable given an automated transmission’s benefits to drivers and the potential for less maintenance and fuel savings.
But you can bet I’d get the programming right.