TROY, Mich. - "Gear jammers" aren't what they used to be, and don't have to be.Today's transmissions are easier than ever to shift, thanks to low-inertia designs and lower clutch-pedal pressures. But ...
NEW FREEDOM: ZF Meritor's new transmission sports includes a twin countershaft with full helical gearing for reducing noise.
TROY, Mich. – “Gear jammers” aren’t what they used to be, and don’t have to be.
Today’s transmissions are easier than ever to shift, thanks to low-inertia designs and lower clutch-pedal pressures. But if you’re willing to spend some extra money, the driver can let the transmission do some or all of the shifting. And there are more products and competition, which increases choices and should hold down prices.
Manual transmissions still account for most sales. But “automated mechanical” products are making believers out of usually skeptical fleet managers. Automatic transmissions, meanwhile, are taking over the medium-duty market and catching on among specialty users.
To be sure, shiftlessness has both merits and price. Everyone knows that automatic transmissions are easier to drive than manuals, and in city traffic can considerably cut driver stress. In certain jobs they also tend to pay for themselves in less maintenance and longer life for the engine and driveline. Fuel economy can be better because while the driver may get tired, the transmission never does. And it always shifts properly.
If you’re thinking of making a move from manual to automatics or automated mechanicals, you have plenty of products to pick from.
Fully-automated, continuous power – A generic description of Allison automatics would be that they are related in principle to those on cars and light trucks. But they are much stronger and more complex.
Allisons use hydraulic pumps, torque converters, gear packs and mechanical or electronic controls to transmit power. Power is continuous during operation.
Allison’s traditional family consists of the AT (for light-medium trucks), MT (for medium trucks) and HT (for heavy trucks, which is no longer available). These use four or five speeds, with top gear being a direct, 1 to 1 ratio. They are now standard with electronic controls, but there are many thousands of older units still out there that have hydraulic controls.
Allison’s more recent World Transmissions include the MD (medium-duty) and HD (heavy-duty) models, which use four, five, six, or seven speeds. The top two gears of many models are overdrive ratios. Allison recently introduced 1000, 2000 and 2400 series products for light- to medium-duty trucks. These have five speeds with an overdrive. Like the MD and HD, the new products come with advanced electronic controls.
Automated, interrupted power (also called the automated mechanical transmission, or AMT) – The transmission’s electronic controls work with the engine’s controls to select and change gears in a mechanical gearbox. Engine power is interrupted during shifts, and shift points are based on terrain, load and driver demand. Recent advances in electronics have allowed engine and transmission to “talk” very fast to each other, making possible the latest AMT products.
Automation can be full or partial, meaning the driver has less or more to do. With full automation, the transmission shifts itself while under way. Automation can also be carried to the clutch, and is with two products. With partial automation, the driver must do much of the shifting or tell the transmission when to change gears. And he still punches a manual clutch, though not as much as with a manual trannie.
Full automation is a feature of several products, and two need a manual clutch for stopping and starting: Eaton Fuller’s AutoShift, which shifts itself completely while under way; and ZF Meritor’s Sure-Shift, which shifts only when the driver taps a lever. These are called “three-pedal” systems because of the presence of a clutch pedal.
Full automation with an automated clutch is used by ZF Meritor’s FreedomLine and TTC’s OptiShift (formerly called the AMT-7). They run themselves and are called “two-pedal” systems because there’s no clutch pedal.
Two-pedal systems can pretty much be driven like a full automatic, but not quite. There is a clutch, and it helps if the driver has some experience driving a manual transmission and understands that he can abuse the clutch under some circumstances – for instance, feathering the accelerator to hold the truck on an upgrade instead of stepping on the brake pedal.
But the facings of automated clutches last longer than those ahead of manual transmissions, say manufacturers.
So there should be a maintenance advantage with them, not to mention easier driving.
Two-pedal AMTs are the next best thing to an Allison. Even three-pedal AMTs are much easier to drive than any manual. However, if something goes wrong, the truck is down until it’s fixed.
Partial automation is used by Eaton Fuller’s Top 2 and Lightning products, ZF Meritor’s SureShift and Engine Synchro Shift (ESS), and TTC’s AutoMate-2. There are differences among them.
The “2” types involve only the top two gears, shifting back and forth between them at highway speeds.
There is no position for the top ratio; the gear pattern includes an “A” spot, where the second-highest gear would be, and the lever stays there as the transmission shifts between 9th and 10th gears in a 10-speed, for example. This helps the driver achieve the best possible fuel economy while cruising.
The Lightning and ESS help the driver “double-clutch” for up- or downshifts by modifying the engine’s speed. It cuts the throttle for upshifts and revs the engine to the right speed for downshifts. This can be done for any gear, not just the top two.
Usually the driver must ask for help.
With the ESS he pushes a slide switch up or down, waits for the engine to respond, then moves the lever to make the switch.
With the Lightning he taps the accelerator for a downshift, then shifts. He shouldn’t have to touch the clutch pedal during shifts with either product, and in fact disables the ESS’s automated system if he touches the pedal.
Both transmissions can be operated like regular manuals. And if the electronics suffer a failure, the trannie can still be driven.
Indeed, die-hard gear jammers can even shut off the ESS and double-clutch their way through the provinces.
Eaton is also working on an AutoShift with a torque converter.
This will offer smooth starts under extra tough conditions, but uses a multi-speed mechanical gearbox and electronic controls. It will replace an earlier product, the CEEMAT (computer-enhanced, electronically managed automated transmission) which worked with mechanically controlled diesels.
Like the late 1980s/early ’90s CEEMAT, the new product is aimed at on/off-road trucks, like dumpers, concrete mixers and trash haulers. With the torque converter (TC) it of course will need no clutch or clutch pedal; but the TC pack is expensive, and will boost its price close to that of an Allison.
Bear in mind that truck builders, not transmission manufacturers, set the price you’d pay. But here are some rough numbers for the premiums over a manual, from highest to lowest:
Allison runs about US$12,000 in a heavy truck, perhaps $6,000 to $7,000 in a medium and $2,000 to $3,000 in a light; then the upcoming Fuller AS-TC a heavy-duty transmission only, and probably priced just under a comparable Allison.
Then come the remainder of AMTs, all for heavy trucks: FreedomLine is about $4,500, the AutoShift is roughly $3,500 and the Lightning you can have for under $900 and finally the ESS, which is only a few hundred dollars.
Obviously, the more you pay, the more automation – and benefits – you get. As suggested above, some of these are more reliable than others, and you need to check out any reputations before plunking down any cash for anything.
The one sure bet, based on decades of operator experience with them, is the Allison automatics (though the newest light-duty models are as yet somewhat untested).
We must also note that Eaton has sued ArvinMeritor over the technology used in the Sure-Shift and Engine Synchro Shift. Eaton claims its patents on electronic automation have been infringed, and has won in court. ArvinMeritor
is appealing, but if it ultimately loses, it may either have to pay licensing fees or drop these products.
Manufacturers say they expect the market to evolve into three segments: One-third of truck buyers will stay with manuals, one-third will go with AMTs, and one-third will use full-blown automatics.