Severe gas mileage issues. My 2019 with same 6.6L engine got 26mpg hwy 19 mpg cityand had 8 speed trans. Brand new 2021 2500hd diesel gets 16mpg hwy and 13 city with the 10 speed Alision. Seems like it doesn't go over 6th gear. I tested with rpm gauge at 60 mph on flat highway in Drive. Dropped shifter to manual and it's in 6th gear not 9 or ten. Also downshifts at speed when foot comes off throttle. Dealership today put on computer 45 minutes, No Codes. Hopefully someone can respond with help. 2800 miles and only trailered a bass boat once at 14 mph hwy. Ugh
Jamiecoyle21
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3,833 Posts
It's the nature of the Ford 10spd "Allison branded in Name Only" transmission. TFLTrucks noted that the L5P went from the best mileage of the big three in 2019 to the worst MPG in the 2020 model year. The only change was replacing the 6spd Allison with the 10spd 10L1000 Ford trans.
Too bad to. Allison had a 9spd set to go into the 2020 model year...
Too bad to. Allison had a 9spd set to go into the 2020 model year...
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3,833 Posts
It's the same trans as far as function and size but they are not interchangeable for brand identity and they do have different torque converters
Where's the cut-away pic of the GM 10 speed? Why does the Ford specs identify 18qt capacity but the GM version has the fluid capacity missing? Why is the weight of the GM missing?
Hopefully Mike L. will chime in with his expertise since I am paraphrasing his post from another forum...
Where's the cut-away pic of the GM 10 speed? Why does the Ford specs identify 18qt capacity but the GM version has the fluid capacity missing? Why is the weight of the GM missing?
Hopefully Mike L. will chime in with his expertise since I am paraphrasing his post from another forum...
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