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Old 08-13-2012, 08:35 AM   #1 (permalink)
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12-Speed Truck Transmission

This is interesting -- a 12-speed transmission that includes a "smart" version of an old feature; free wheel coasting:

Green Car Congress: New Detroit DT12 transmission contributes to enhanced fuel efficiency and performance for heavy-duty trucks

The picture also shows a oil pump for the transmission:

Chrysler has 8-speed transmission (with 9-speeds coming?), so plain ol' 5-speeds are so ... 20th century.

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Old 08-13-2012, 11:21 AM   #2 (permalink)
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  • Direct Drive. In top gear the transmission operates as a direct drive, sending engine input directly to the main shaft, eliminating parasitic gear mesh losses of power and fuel efficiency.
  • Oil Pump. An oil pump, powered by the countershaft, delivers oil directly to the gears. This is more precise and efficient than bathing all of the gears in oil.
Would these two points imply that in top gear not only are parasitic gear losses eliminated, but also losses from the oil pump?

Ah, I remember when a 10-speed was THE bike. Then came 18-speed mountain bikes, 21-speeds, 24, 27, and then I got lost
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Old 08-13-2012, 12:24 PM   #3 (permalink)
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Originally Posted by NeilBlanchard View Post
Chrysler has 8-speed transmission (with 9-speeds coming?), so plain ol' 5-speeds are so ... 20th century.
Look again. This is for heavy trucks, where 10 or more gears (plus a 2-speed rear end) has been the norm for decades at least.
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Old 08-13-2012, 02:20 PM   #4 (permalink)
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Originally Posted by jamesqf View Post
Look again. This is for heavy trucks, where 10 or more gears (plus a 2-speed rear end) has been the norm for decades at least.
Exactly. There two factors that have contributed to this: 1) The need to accelerate and decelerate very large payloads 2) The heavy duty trucking industry pays more attention to fuel economy than probably any other sector.
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Old 08-13-2012, 04:55 PM   #5 (permalink)
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On a big rig the losses from a transmission oil pump would be minuscule.

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Old 08-13-2012, 11:22 PM   #6 (permalink)
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This trans is, as noted, more about a clean sheet approach to being an automated manual transmission with more sophisticated shift algorithms than with big truck automatics of the recent past. There are variants of what is a big truck "automatic transmission".

Suffice it to say that fleet owners are the ones interested. A "real" truck driver, with five or more years of experience already has the ability to chose the right gear at the right time despite the vagaries of road, load, weather and traffic. (Each of these is worthy of study in depth. The combinations of these puts the lie to the classification of truck driving as "unskilled" labor by the US Dept. of Labor).

Years back one had two transmissions and sometimes a two speed rear axle. Three sticks to control. Multiple times. In more recent decades the usual fleet transmission has been either a 9 or 10 speed (effectively, an 8 or 9 speed plus a granny low).

The 2012 367 Peterbilt I drive at present has an EATON 10-speed. I often wish for a 13-speed, but they take more attention, and more finesse. An automated 12 is an obvious way of cutting some tenths for most fleet trucks. I often spend a great deal of time moving between the top two gears as they cover such a wide range of travel speeds. A 13 would give me more control over engine rpm (shorter rpm range between shifts, say a 250-rpm rise).

Being able to split the "high range" of the gearbox would really be great. But the sheer number of choices when descending a curving piece of shiny, wet asphalt loaded to 74k into an intersection can be too much when one is new. How many gears to drop, and how long to pause between gears [as well as steer, brake and visually command the scene) is something only experience can do for a driver.

An automated manual is the obvious future for what is needed for reliable predictable big truck fleet fuel consumption. And not compromise safety or the load.
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Old 08-14-2012, 10:13 AM   #7 (permalink)
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Could you imagine if regulr drivers had to learn to split shift
How about one of the old Rockwells in a SUV going to soccer practice
"unskilled" my left foot
that said, ive driven ta midsize with an autostick and it makes for less stressfull driving in town

I can't understand why my MPG's are so low..........
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Old 08-31-2012, 02:40 AM   #8 (permalink)
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big rig manual tranys that shift them selves are all ready on the market
Eaton moves Fuller UltraShift 10-speed to full production

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