Allison debuts radically different 10-speed automatic transmission

Allison Transmission on Wednesday, Sept. 14, introduced to the press a radically different 10-speed fully automatic twin-countershaft range-type truck transmission called the TC-10 intended for use in truck tractors. Allison says that production will begin on Oct. 1, 2012, and will ramp up to maximum levels by 2013. Several protoype transmissions presently are being tested in fleet operation.

Like all other Allisons, the transmission will have a torque converter with lockup clutch in place of a standard dry clutch at front. But it will have helical gears integrated with a twin-countershaft layout for the 5-forward speeds and the reverse gears in the main box, as well as a two-speed planetary range box at the rear. The transmission is new from the ground up, including the torque converter.

Todd Dygert, NAFTA-MSS product specialist for the TC-10, said all the shifts will be made through five multiplate wet clutches similar to those used in other Allison automatics, one of which will serve to handle range shifts. Dygert described the unit as having “blended architecture,” combining characteristics of the twin-countershaft mechanical truck transmission with those of present Allison automatics.

Andy Osterholzer, marketing specialist, said the transmission will provide continuous power application, although the power level will be reduced slightly during shifts to cushion them. Acceleration is much faster because when power flow is continuous, the turbocharger does not have to spool back up after shifts. Drivers will notice that shifts occur quickly – much more so than with an automated manual – yet smoothly. Engine brake operation also will apply torque continuously even when the transmission is downshifting.

The transmission’s torque converter multiplies engine torque by 1.76 at startup, which allows use of a taller first gear than other 10-speeds. This provides a smoother launch as well as the ability to offer much closer gearsteps – especially between 8th, 9th and 10th gears – than standard 10-speeds. The steps between 8th, 9th and 10th gears are only about 17 percent versus about 34 percent in typical 10-speeds.

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These close gear ratios allow the transmission to shift freely without excessive wear to the clutches. This means an 80,000-pound tractor-trailer can be geared for an unusually low cruise rpm – 1,200 at 65, perfectly suitable for level road cruise. As soon as more power is needed for hill climbing or acceleration, the transmission will shift almost imperceptively down to 9th.

The transmission will save a considerable amount of fuel, partly due to its ability to allow lower cruise rpms and also because there is an inherent loss during the power interruptions that occur with all standard mechanical transmissions. Further, productivity will be improved, especially in applications where there are frequent stops and starts.

Maximum power and torque ratings will be 600 hp at 1,850 lb. ft. The unit will have an aluminum case and will weigh 1,030 pounds without a PTO, compatible with a 13-speed automated transmission. Fluid and filter change intervals will likely be set at 500,000 miles when the proper synthetic automatic transmission used. The unit will have a 5-year 750,000-mile warranty.