Heavy Duty Trucking

AUG 2014

The Fleet Business Authority

Issue link: https://heavydutytrucking.epubxp.com/i/364502

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Page 41 of 109

start missing shifts, overrevving the engine, and wasting fuel. That's why automated transmissions are catching on in heavy trucks, although with most you can still feel the power be- ing transmitted mechanically. Another look A few weeks earlier, I took another TC10-equipped ProStar on a longer jaunt out in the countryside. A couple of Allison marketing people rode along as we departed from Indianap- olis via Interstate 65, cruising south to Indiana 46, west to Bloomington and Indiana 37, then north and back to Allison's premises. Highway 46 has some short but steep hills that begin at Nashville, a touristy town in scenic Brown County, so it's a good test of an engine's power and a self-shifting transmission's ability to pick the cor- rect gear for a situation. From a dead stop, the TC10's torque converter launched the vehicle authoritatively. The converter multi- plies torque to increase the effective- ness of 1st gear's otherwise tall 7.4:1 ratio. The converter locks up right away to boost efficiency all the way to cruising speed. Ninth gear is 1:1 direct and 10th is a 0.86:1 overdrive. Rolling terrain caused the transmis- sion to shift often between 9th and 10th, but usually I didn't notice unless I looked at the selector's LED readout. Thanks to load and incline sensors on the chassis, its Generation 5 elec- tronic controls and careful matching to those of a 12.4-liter, 475-horse- power Navistar MaxxForce 13, the higher gears. For a driver who wants to know what the transmission is doing, a readout on the Allison's keypad will tell him, as it did me. For instance, 10/1 means 10 gears are available and it's about to start out in 1st, or 10/9, that it's in 9th-direct and any time Circle 214 on Reader Action Card now will upshift to 10th-overdrive. The "shift-it-himself " driver knows there is joy in feeling the power course through each gear and satisfac- tion in making those changes all by himself, assuming he does it correctly every time. However, very few drivers can, especially when they tire out and 40 HDT • AUGUST 2014 www.truckinginfo.com test drive PHOTO: TOM BERG The push-button shift selector is like those for Allison's traditional 6-speed automatics. Readout shows the TC10 has 10 ratios available and we're about to start out in 1st gear.

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