Understanding The AutoShift
It won't be "balky' if you know exactly how to operate it, says a guy who does.
Back in our August HDT we ran a Drive Test article on a '99 Freightliner Century Refurbished Daycab, a renewed used tractor that I said had a lot going for it - except that its Eaton AutoShift transmission sometimes didn't want to go into gear.
I wondered what might be wrong with the "balky" tranny and speculated that something electronic might be to blame. Not so, according to the fleet executive who originally ordered that tractor.
Marty Fletcher, vice president of technology for US Xpress Enterprises - a fleet that has completely converted over to automated mechanical transmissions - was at the Used Truck Assn.'s convention last October in Arizona.
He was showing off a later-model tractor to attendees, and I climbed aboard and repeated my tale of woe:
"Right after starting the engine, the AutoShift sometimes failed to go from Neutral to Drive or Reverse unless I played with the controls or tapped the brake pedal," I told him.
He immediately diagnosed the problem.
"The transmission's input shaft was most likely still spinning, and it won't go into gear until the shaft has stopped spinning," he said. "The electronic controls wouldn't let it. I'll bet that the times when it did go into gear, you had coincidently kept your foot on the pedal longer, so that the shaft had time to slow down and stop. Or you had pushed the pedal down far enough to engage the clutch brake."
"Aha!" I said.
"And I think I can re-create the problem right here," he continued.
This tractor was a Volvo VNL, but its 10-speed AutoShift was the same as the one I had driven. He pushed the clutch about three-quarters of the way to the floor and quickly slipped the selector lever to D, and then to R. Sure enough, it wouldn't engage. When he punched the pedal all the way to the floor and again selected D and R, the transmission engaged promptly.
"Well, I'll be," I said.
Then I asked about another AutoShift complaint I heard from a US Xpress driver several years ago. AutoShifts were a new thing with the fleet back then, and the driver called me to say that he couldn't get the transmission to downshift enough to raise engine revs and take full advantage of the Jake brake. It annoyed him because the truck wasn't as safe as it should've been while descending long mountain grades.
"That tells me we didn't do a good job communicating to that driver how to operate the truck," Fletcher said.
Then he explained how it should be done: The way to prompt a maximum-performance downshift is not by thumbing the "down" arrow on the selector's T-handle, as I had suggested to that driver. Yes, the arrow will cause a downshift, but it will be conservative and the engine will be well under its redline.
Instead, you simply pull the selector into Low. If the electronic brain figures it can downshift without overrevving the engine, it'll quickly order the shifter servos to grab the next lower gear, meanwhile raising rpms right about to governed speed. And it'll keep downshifting, letting the Jake work hard all the way into 1st if you want the truck to slow down that much.
He demonstrated with the Volvo, which he was bobtailing around a parking lot so he could concentrate on his instructing without worrying about a trailer. At about 20 mph and 5th gear, he pulled the selector into Low and the Autoshift began gearing down, raising engine revs high and letting the Jake slow us to a crawl. Every downshift was flawless and fast - smoother and faster than most drivers could ever do 'em.
So, although the AutoShift can make a driver's job easier, he or she needs to know how to get the most from it and avoid glitches like I ran into, Fletcher said.
I got a lot out of Fletcher's instruction, and now I wouldn't think twice before buying a truck with the AutoShift.
—Tom Berg, Equipment Editor
