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Author Topic: Allison Power Losses  (Read 855 times)
TomC
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« on: January 12, 2007, 03:18:47 PM »

I just had a converstion with our Allison Factory Sales rep, and he just verified what I had been saying all along about the effieciency of the Allison compared to a manual transmission.  The Allison will naturally loose 1/10 to 2/10 mpg right off the bat because of the spinning losses as compared to a manual transmission.  Where the main difference in mileage occurs is that most Allison owners just floor it all the time.  For normal around town driving, try not to use more than 1/2 accelerator pedal, and your mileage will increase.  The Allison rep also said, that the Allison will get better mileage when compared to someone that doesn't know how to shift a manual transmission.  Thought you'd like to know.  Good Luck, TomC
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Tom & Donna Christman. '77 AMGeneral 10240B; 8V-71TATAIC V730.
Beatenbo
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« Reply #1 on: January 12, 2007, 09:07:06 PM »

I hear what ya say Tom, but I've never had an AT that would shift right at half throttle. The smoothest shift is at full RPM. Just my experience.
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TomC
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« Reply #2 on: January 12, 2007, 10:32:24 PM »

Rough shifts at part throttle are common place with mechanically controlled autos.  Now with electronic controlls, they are very smooth.  I know they're rough since I can get torque converter lockup with my V730 as low as 20mph-and you can feel it bump in.  Good Luck, TomC
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Tom & Donna Christman. '77 AMGeneral 10240B; 8V-71TATAIC V730.
captain ron
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« Reply #3 on: January 12, 2007, 11:11:34 PM »

When I try to operate at lower rpm's my tranny shifts back and forth between 3rd and 4th gear really bad and it annoys me. I will then either speed up or manually shift. 8v92 DDEC 740A ATEC
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TomC
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« Reply #4 on: January 13, 2007, 08:32:38 AM »

I personally leave my shifter in 2 (or 3 for the HT740) until I get to freeway speeds. Then shift it up so it can't hunt.  Good Luck, TomC
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Tom & Donna Christman. '77 AMGeneral 10240B; 8V-71TATAIC V730.
buswarrior
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« Reply #5 on: January 14, 2007, 07:52:05 PM »

Hello all.

No commercial coach driver worth his or her salt ever left an HT 740 unsupervised to do its own shifting.

Part throttle hunting between gears is not the path to happy passengers.

Around town, leave the shifter in 2nd, the 740 may be trusted to behave between 1-2 and 2-1.

You make the rest of the shifts, and then you may start saving fuel and giving a better ride to the co-pilot and the dishes by accelerating lightly up to the speed that the 740 will not bang up and down between gears.

For instance, in mine, the governor in 2 is at an indicated 37 mph, 3rd gear will only hold full throttle above 31 mph, but the 740 will upshift to 3rd in the mid 20's under light throttle, setting the stage for a rough downshift if any speed is lost or any further throttle is applied.

Similiarly, when losing speed on a climb, force the downshift just as speed reaches the governor for the next lower gear to maximize what little climbing power we have.

Moral of the story, don't allow the 740 access to the next gear on the way up, and force it on the way down.

happy coaching!
buswarrior
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Frozen North, Greater Toronto Area
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