Eaton’s soon-to-be-released Procision medium-duty transmission was unveiled at the company’s Marshall, Mich., proving grounds in September.
Several Freightliner M2 Business Class trucks with the Procision were on hand, loaded with about 8,000 pounds. A similar truck was equipped with an Allison 2000-series RDS — the automatic transmission that currently dominates this market and from which Eaton hopes to capture a significant chunk of market share.
The Procision transmission is a 7-speed dual-clutch design that Eaton says will save fuel and provide a driving experience similar to an automatic-equipped car.
I found several attributes the Procision had over the competitor, mostly in the low-speed maneuverability category. Most obvious was the performance on hills. We tested the transmission on several grades: 3%, 5%, 8%, 10%, 15% and finally 20%. You won’t find many 15% or 20% grades in the real world, but 8% or 10% aren’t uncommon around loading docks and parking lots.
When descending any of those grades, the clutch engaged fully and took advantage of what engine-compression retarding there was.
The engine won the day against 8% and lower grades, keeping the truck at a reasonable speed in 1st or 2nd gear. It was easily overwhelmed by the 10% or higher grades, which forced the engine to request an upshift to protect itself from overspeed.
The torque-convertor-equipped transmission basically just freewheeled down the hill, and required a pretty stiff brake application to keep it reigned in. The Procision, however, was far more under control.
Upward bound, the Procision managed to idle up even the 8% grade, mustering enough torque through the clutch plate to maintain forward movement. The automatic managed the 5% grade, but no more.
In tight maneuvers, like docking or parking, the Procision transmission “feathers” its clutch to maintain a very low creep speed. Eaton calls this “creep mode,” and the actual speed is a customer-programmable parameter. With the engine at idle speed, the degree of clutch engagement varies with vehicle speed. It works equally well in forward or reverse, and toggling between forward and reverse can be done while the vehicle is moving with no adverse effects. It doesn’t clunk into the next gear, or require the vehicle to stop completely before initiating the direction change, as is the case with some automated manuals.
Finally, on the oval part of the track, we had a chance to see how the transmission worked at speed, under acceleration and deceleration. Shift schedules corresponded to power demand, swinging from low rpm during leisurely acceleration to near red-line under full power acceleration. Generally, they were on the lower side of 1,600 rpm, which isn’t bad for a 6.7-liter engine.
I played with the accelerator pedal, alternatively gunning the engine, backing off, braking, etc., to see if I could fool it into a mis-shift. I failed. The Procision found the right gear nearly instantly each and every time. While coasting, Eaton says, the driver has only to tap the brake pedal to initiate a downshift. I found it took a bit more than a tap, bordering on a stab, but downshift it did, engaging the engine brake (an exhaust brake in this case) to provide gentle, brake-saving deceleration.
Based on these first impressions, the new Procision should be a strong contender in the medium-duty market. Deliveries begin next July.