In about 13 months, buyers of heavy-duty road tractors will have another transmission choice: Allison's TC10, which combines a torque converter with a sophisticated 10-speed mechanical gearbox to achieve easy starts and smooth, fast shifting.

It will provide performance and fuel economy superior to that of competitors' products, company representatives said at an unveiling this week at their Indianapolis headquarters.

More properly called TC10 TS (for tractor series), it will be aimed primarily at short-haul and regional tractors that run on-highway but see a lot of gear shifting, as well as some vocational tractors that don't go off road, said Todd Dygert, a product specialist.

As a transmission for Class 8 tractors, the TC10 will complement but not replace Allison's fully automatic 4000 RDS (rugged duty series) transmissions that see on/off-road service in straight trucks. The 4000 HS (highway series) works well for some heavy on-highway applications but is not a good fit for long-haul road tractors, said Jim Wanaselja, vice president for North Ameircan sales and service. But the TC10 will be.

Inside the TC10

Along with "torque converter," TC in the name also means "twin countershaft," the main gearbox's mechanical layout. Power flow alternates among the counter- and main shafts, depending on what gear it's in, Dygert explained.

Engine power is continuously delivered via wet clutches -- five in the main 5-speed gearbox and two in the 2-speed range box. The range box also uses planetary gears and a synchronizer for forward to reverse shifts. "Power shifting" means a constant flow of power and torque during gear changes, which contributes to brisk acceleration.

The TC10's main competition will be Eaton's UltraShift Plus 10-speed, an increasingly popular automated mechanical transmission whose power-interrupt shifting is seen by Allison people as a detriment to both performance and economy. The Volvo/Mack I-Shift/mDrive operate similarly. Each power pause causes the vehicle to momentarily lose momentum that the engine must then recover, burning an extra bit of fuel each time, Allison people contend.

Durability and cost were among development goals, Dygert said. TC10 will be warranted for five years and 750,000 miles. All components, including the wet clutches, are intended to last the life of a transmission. The only scheduled maintenance is a changing of the synthetic fluid at 500,000 miles.

It will initially be rated for use with engines making up to 600 horsepower and 1,650 pound-feet, he said. A higher torque rating will follow.

Looking Ahead

Early development and demonstration units now running have straight-cut gears, but production TC10s will have helical gears with quieter angled teeth. Six TC10s are now being evaluated by customers in regular service, Dygert said.

The TC10 will be sold to truck original-equipment manufacturers for less than an Allison 4000, and at a price targeted to be competitive with existing automated mechanical transmissions. "Competitive" means acquisition cost plus value, representatives said, noting that OEMs always set final component prices.

Allison will assemble the TC10 at its Indianapolis complex using its own parts and some from suppliers. Sources will be determined between now and production launch. It expects the product to qualify for Buy American requirements in government orders, meaning the majority of its components will be made in the USA, said Melissa Sauer, director, government and community relations.

Because the TC10's control module communicates via a J1939 data bus, it will work with any electronically controlled on-highway diesel, said Steve Spurlin, executive director, application engineering and vehicle integration. Allison expects to be working with most major OEMs as production begins in October 2012 and ramps up in 2013.

Because it's more than a year away, why announce it now? "To expose it to a market that we're not now in," answered Spurlin.

Exposure has begun.