Eaton has worked with truck makers for several years to tailor each UltraShift Plus model into an integrated powertrain configuration designed for specific applications.
There are seven models in the Plus range, in three application-specific families: linehaul, vocational and multi-purpose heavy-haul. While the fundamentals remain the same across the models, electronics offer a variety of performance characteristics, from a sweet-shifting and very tame linehaul box to vocational and high-performance set ups that will climb any hill, or creep along under full load at a less than a walking pace.
Inside the transmission
The most apparent change is the replacement of the centrifugal clutch and fully float-shifted gear change with a conventional-style two-plate ceramic clutch operated by an electronically controlled electric motor. The electronic clutch actuator mechanism (ECA) is a robust motor/planetary gear that sits in the clutch housing. The ECA is slave to the transmission and connects through its own communications, not J1939. The transmission itself communicates with other vehicle systems through J1939.
Also located in the bell housing is Eaton's signature inertia brake. It replaces the simpler but primitive clutch brake.
The use of electronic controls and the conventional clutch means the transmission is a true two-pedal automated transmission, but one that behaves much more like a conventional three-pedal one. In contrast to the previous UltraShift, the Plus can be very well controlled from the throttle pedal, where a light touch brings a partial engagement of the clutch. This makes tasks such as trailer coupling and creeping back into the loading dock much more controllable and predictable.
A couple of other new features include a gear-hold creep mode that allows a driver to select a gear that will hold and allow for creeping along in heavy traffic. The feature also allows for low-speed operation in vocational applications such as pouring concrete for curbs or spreading asphalt.
How it works
The electronic controls for the shifting sequence are much more refined than in previous models. The transmission calculates the weight of the truck and also senses grade, both starting out and on the fly. It is also sensitive to pedal position, so it can respond with economy or performance shifting, without any button selection by the driver. Also included to help the driver is a hill-start aid that will hold the truck stationary for up to three seconds as throttle is applied on a hill start - heading up or down a grade.
The shifts in the lower gears are completed with the aid of the clutch. In the lowest gears, the inertia brake allows for very quick shifts. This combination, plus the fast calculations on the control module that senses torque, throttle, weight and grade, mean a fast progression through the gears, often skipping shifts for optimum performance. Situations such as accelerating on an onramp or up out of a pit are handled exceptionally well in this latest version of the UltraShift.
The driver interface is through the familiar keypad, or through the Eaton seat-mounted "cobra-head" shifter, or through proprietary shifters from the truck makers.
With its grade sensor, after learning the weight of the truck, the transmission selects a starting gear. That can be overridden if the driver selects manual mode. Once in manual, the transmission holds the selected gear unless automated mode is selected or the driver bumps the gear up or down using the shift buttons.
The UltraShift Plus was intended from the start to be a range of transmissions that would handle all applications with no compromises. So the toughest situations were addressed first: Controls had to accommodate vocational transmissions with low-low gears.
This also meant designing a clutch that would be extremely robust for these applications. The starting point was the clutch used in roadtrain operations in Australia, where gross combination weights of 250,000 pounds and more have to be started. Initially, several clutch designs were considered for different applications, but it was decided that that same robust design would be used in all iterations of the UltraShift Plus. Dump and mixer applications have a six-year minimum design life, and other applications can expect a clutch life of eight years or more.
Since the clutch is electronically controlled, it sees an absolute minimum of driver abuse.
Numerous protections and fail-safes are built in to the UltraShift Plus. One is the elimination of the torque-lock. This proved to be a problem on earlier transmissions, for instance if keyed off in gear when backed up to a dock. When the brakes are applied by the dash valve, or if the spring brakes dynamite, the transmission goes to neutral. Eaton engineers say that in four years of development work there has not been an instance of torque lock with the new control system.
Another Plus feature is auto-engage in a downhill start. As the truck starts to roll - once hill-hold has been disengaged by the throttle, or after the three-second hold period expires - the transmission immediately picks up a gear so the truck never free-rolls from a start. Engine overspeed and underspeed are protected when a driver attempts to override the automated gear selection.
When the engine retarder is selected, the transmission goes to a more aggressive downshift sequence to maximize braking performance.
The basic transmissions and the X/Y shifter are the well-proven Eaton Fuller transmission components and present no new challenges in service. There is an additional opening in the gearcase for an additional PTO. The transmissions now have three: bottom, side and top.
If a technician can deal with electronic engines, the new UltraShift Plus should pose no problem, says Eaton. The ECA is extremely robust and is expected to outlive the useful vehicle life, but the assembly is easily removed from the clutch housing without needing to swing the transmission.
The transmission has already seen limited release in the tough and abusive applications of Australia, South Africa, Brazil and China. It is due for limited release at truck OEMs here beginning in October. The transmission has been matched to all available engines, including the Paccar MX due for release toward the end of 2010.
Pricing is set by the truck maker, but Eaton is not expecting any radical pricing for the automated transmission. It is likely to cost less than an Allison in applications such as vocational, too.
On the road - and off
Driving demonstrations at Eaton's proving ground in Marshall, Mich., and on nearby urban and highway sections showed the transmission presents a paradigm shift from the previous UltraShift. The on-highway LAS model was sensitive to throttle demand and would upshift nicely and progressively, even when we were driving bobtail. Once truck weight had been learned in the first couple of shifts, the transmission could be left to shift early in the rpms with a light throttle. It was sensitive to driver manual control, too, if the upshifts were commanded earlier in manual mode (unless the shift would drop the engine below its design speeds).
Hill starts were a charm using the hill-hold. The truck - a Volvo 485 D13 - sat until the throttle was touched. The clutch engages very smoothly and the truck begins to creep forward. Coming off the hill start, the transmission upshifted. Once