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Discussion Starter #1
My recent towing experience indicated there's an issue with the shift points on the 4x2 Duramax 1500. When first starting out the tranny held 1500 rpm and shifts to 1800 on inclines. Occasionally it would kick down to 8th @2200 rpm. My return trip bothered me because it wouldn't shift up but kept 2200 most of the trip home. Any hill would cause the tranny to abruptly shift up to 3000 rpm and it would hold there even after getting off the throttle.
Just wondering if anyone else has experienced this issue. I have appointment with dealership in two weeks.
 

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My recent towing experience indicated there's an issue with the shift points on the 4x2 Duramax 1500. When first starting out the tranny held 1500 rpm and shifts to 1800 on inclines. Occasionally it would kick down to 8th @2200 rpm. My return trip bothered me because it wouldn't shift up but kept 2200 most of the trip home. Any hill would cause the tranny to abruptly shift up to 3000 rpm and it would hold there even after getting off the throttle.
Just wondering if anyone else has experienced this issue. I have appointment with dealership in two weeks.
The Duramax 1500 does not have the Allison 10 speed.
 

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Discussion Starter #5
Actually it does. That's one of the selling points of the new 1500 I-6 Duramax. The 5.3 has the option of the 8 or 10 spd .
 

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1500 - 3.0L with 10L80
2500 - 6.6L with 10L1000


Not sure why the included the ratios for 8, 9 and 10 on the same line -- but they did it for both transmissions.

GMC Sierra /Denali 1500
MQB 10-SPEED AUTOMATIC TRANSMISSION SPECIFICATIONS
Transmission model
AUTOMATIC 10-SPEED HYDRA-MATIC 10L80
RPO Code
MQB​
GEAR RATIOS
First​
4.69​
Second​
2.98​
Third​
2.15​
Fourth​
1.8​
Fifth​
1.52​
Sixth​
1.28​
Seventh​
1.0​
Eighth​
0.85, 0.69, 0.63​
Reverse​
4.86​
TORQUE CONVERTER
Element types​
Variable force solenoid TCC, Centrifugal Pendulum absorber (CPA)​
Maximum Engine Torque (lb-ft/N-m)
627/846.45​
LUBRICANT CAPACITY (pints/litre)
Fluid Capacity​
26.5/12.5398​
MAX GVW(lbs/kg)
6450/2925.72​
MAX GCWR(lbs/kg)
7460/3383.856​



GMC All-New Sierra/Denali 2500 HD
MGM/MGU 10-SPEED AUTOMATIC TRANSMISSION SPECIFICATIONS
Transmission model
AUTOMATIC 10-SPEED ALLISON 10L1000
RPO Code
MGM/MGU​
GEAR RATIOS
First​
4.54​
Second​
2.866​
Third​
2.06​
Fourth​
1.72​
Fifth​
1.48​
Sixth​
1.26​
Seventh​
1.00​
Eighth​
0.85, 0.68, 0.63​
Reverse​
4.54​
TORQUE CONVERTER
LUBRICANT CAPACITY (pints/litre)
Fluid Capacity​
41.21/19.500572​
MAX GCWR(lbs/kg)
40000/18144​
 

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The 10 speed behind the LM2 is the same trans as the 10 speed that is behind the 6.2L gas engine. Just different TCM calibration and torque convertor.
 
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The 10 speed transmission in the gassers are a love child of Chevrolet and Ford. The trucks have the same transmission but most likely different wiring harnesses. That was the main reason I went with diesel again (emissions equipment and all) over the gassers cause I have worked on enough ford transmissions to know they are junk. But it goes back to that old saying "you have to pay the cost to be the boss" lol
 

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Discussion Starter #10
Research shows the new Silverado 1500, 3.0 Duramax has an Allison Badged 10L80 10-speed Transmission...Getting back to my original question; Has anyone else experienced the issue with the transmission hanging in low gear hauling a trailer in the hills? I understand there is an adaptive learning procedure for this tranny and from what I have seen it can only be performed at the dealership. I just dumped my 2015 Ram Ecodiesel due to service related issues like; engine fire @ 43000 miles and the ZF80 transmission cratering @ 68700 miles. Both left me stranded on vacation. With a custom tune from SKT I was avg 14 - 17 mpg hauling my 5800lb (loaded) toyhauler. So far I am not impressed with the Silverado. I towed 830 mile loop from Abilene to Poteau OK and avg 13.8 mpg going out and 11.3 return on mostly interstate. I run 65-70 mph same as with the Ram...
With a stronger engine than the RAM I was anticipating my mileage in the 15-18 mpg range. I tow about 5000 miles during the summer so a 5 mpg difference can mean a 300 mile range difference in my trip as well as additional $$$.
[11.5 mpg = 115 miles on 10 gal. 18 mpg = 180 miles on 10 gal. That's a 65 mile difference that adds every fill up.]
 

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I hate to be the bearer of bad news (or maybe good lol) but your transmission is a GM and Ford co-developed tranny and NOT a rebranded Allison.
But EVERYONE wants to say they have an Allison xmsn 🤦‍♂️
 

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The Ford/GM co-developed 10 speed is the one in the 1500, not the one in the HD's.
 
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Ford/GM Co-developed one:

David Ames (GM assistant chief engineer showing / discussing the Allison branded one at the unveiling in Flint:
Developed by GM and Allison

About 2:30 he verifies GM/Allison for the HD vs GM/Ford for the LD one.
 
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