?We also offer a ?C? ratio 10-speed, which is essentially an on-highway transmission, but with a good overall ratio that can manage many dump truck duty cycles,? he continues. This can be an economical choice for the application, but care must be taken not to over task the transmission.
?Our 13-speed has been used for many years on construction sites, as well as our 15-speed with five low gears and 10 road gears,? DeVito notes. Then there is the 18-speed, which is available in manual and automated versions. ?An 18-speed is preferred for heavy hauls in excess of 90,000-lb. GCW because of its ability to split gears for improved performance in the low end.?
If you haul heavy loads, you may want to consider a transmission with more speeds, because you get closer splits between each gear. ?When considering a heavier load, an 18-speed transmission would make sense,? says Daniels.
Another advantage of manual transmissions is the initial purchase cost. Because of their simple design, they tend to cost the least. However, they have disadvantages when it comes to vehicle launch, torque interruption, driver pool and driver fatigue.
?Driver pool experience has been shown to limit the ability of a fleet to operate manual transmissions,? Daniels notes. ?Inexperienced drivers may not be operating the vehicle at its optimal performance and efficiency, therefore reducing fuel economy, clutch life, etc.?
AMTs add ease of operation
This is where an automated mechanical transmission (AMT) can be a plus. An AMT is based on a mechanical transmission, but the necessary electrical components have been added to take operator experience out of the equation. ?This concept takes a base manual transmission and adds an automated clutch, shift controls and computer logic to its operation,? says DeVito.
AMTs come in both two- and three-pedal designs. The three-pedal design incorporates a clutch pedal for launching the vehicle. The two-pedal system launches the vehicle automatically without a clutch pedal.
Once in motion, an AMT operates like an automatic transmission, yet promises the efficiency of a manual transmission. It uses information from the engine to efficiently perform shifts.
?Fuel economy is more important than ever before and all of the fleets are looking for an edge,? says DeVito. ?With the advent of AMTs, the fleet can now spec the convenience of an automated transmission that features the fuel economy of a perfectly shifted, multi-speed transmission.
?Fleets currently using AMTs report a reduction in training time and greater operator satisfaction and productivity,? he adds. ?Also, taking the manual transmission out of the truck will often provide you with a broader pool of prospective operators, including those that may have a difficult time learning to shift a manual transmission with 10, 13, 15 or even 18 speeds.?
There are also benefits even with experienced drivers. ?Though seasoned drivers may state that they want to control all their shifts, this can result in poorer performance and efficiency,? says DeVito. ?When a fleet equips their trucks with AMTs, all the operators shift as efficiently as their best driver.?
In addition, DeVito claims the AMTs increase fuel efficiency vs. an automatic. ?The torque converter in an automatic takes some time to ?lock up,? or establish a direct connection with the rest of the drivetrain. The result of that action is wasted power and fuel, at least until lock-up occurs,? he states.
The other difference is the number of speeds available. ?In a heavy-duty dump truck with an automatic transmission, the operator has only five or six speeds. In an AMT, the operator may have 10, 13, 15 or 18 speeds that the transmission computer selects as the ideal ratio for that moment,? Daniels points out. ?When gear ratios are more closely controlled across a wider variety of choices, the result is improved performance and fuel efficiency.?
Until recently, the selection of AMTs for on/off-road use was limited. ?Today?s automated products can be limited by clutch availability at these high weights,? says Daniels. ?Continued improvements in clutch technology are under development and will benefit the penetration of AMTs in off-road applications.?