[ms14796]

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.

 

[lavarock]

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.

 

[ms14796]

2020 Silverado I-6 1500 Duramax.

 

[lavarock]

2020 Silverado I-6 1500 Duramax.

I was confused about what truck you have.

The 1500 Duramax does not have the Allison 10 speed. So I thought you may have mistyped the 1500 when you should have typed 2500.

 

[ms14796]

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 .

 

[rockn69]

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 .

It's not an Allison, its a hydramatic 10L80

 

[redwngr]

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​

 

[ChevyTech77]

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.

 

[ChevyCowboy2013]

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

 

[ms14796]

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.]

 

[m1lkman1974]

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.

To answer your question, I have not read this anywhere in the forums so far.

Here is the information breakdown of your tranny.. GM Hydra-Matic 10L80 10-Speed Automatic Transmission

 

[407driver]

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 🤦‍♂️

 

[redwngr]

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

 

[redwngr]

Ford/GM Co-developed one:

Holy Shift! A Look inside GM’s new 10-Speed Automatic

Engineers for the new 10-speed automatic transmission available in the 2017 Chevrolet Camaro ZL1 built on the experience of previous, critically acclaimed Hydra-Matic multispeed transmissions to push its performance, refinement and efficiency advantages to a new threshold.

media.gm.com

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.

 

[ms14796]

I now have 5000 miles on the truck and recently started noticing engine surging at intersections with cold engine/transmission. Transmission shifts rougher as well when cold. One other issue I noticed is the hang from 1st - 5th gears. I tend to drive easy on the throttle so I noticed the transmission will hang at its shift point for a few seconds before finally shifting. Even if I ease off the throttle it just sits there around 2000 rpm and then abruptly shifts. I never had that issue with the Ecodiesel 8 spd. As soon as I eased off the throttle it would shift up.
I'm going to contact the local dealer transmission specialist and see what he thinks.

 

[Jonnerns]

I now have 5000 miles on the truck and recently started noticing engine surging at intersections with cold engine/transmission. Transmission shifts rougher as well when cold. One other issue I noticed is the hang from 1st - 5th gears. I tend to drive easy on the throttle so I noticed the transmission will hang at its shift point for a few seconds before finally shifting. Even if I ease off the throttle it just sits there around 2000 rpm and then abruptly shifts. I never had that issue with the Ecodiesel 8 spd. As soon as I eased off the throttle it would shift up.
I'm going to contact the local dealer transmission specialist and see what he thinks.

Did you get any feedback from the dealer? I have the same issues. It's reluctant to upshift and runs way to low gears when towing, especially in slight inclines.

 

[ms14796]

After numerous conversations with the dealership I finally got the service manager to go on a ride. First thing he noticed was the loud whining and then the surging. Pulled the transmission and found the torque converter and the pump housing were toast. So they overhauled the transmission. Next they located a Canbus defect in the tailpipe pressure sensor under the passenger seat. So replaced sensor and canbus along with the clamp on the tailpipe that got broken.
I took a 3 month RV trip hauling my toyhauler up to Reno and Spokane. I started getting an error about a pressure differential in the exhaust. No one in Reno was able to get it checked out until Spokane. Buick dealer knew exactly what the problem was and fixed it.
I don't understand why GM would place a high speed rear axle in this truck knowing folks are going to be towing trailers. My RAM Ecodiesel got better towing mileage vs the GM. As long as I don't have a headwind I'm Golden. I drove south on level ground with a 15mph 1/4ing headwind and watched my fuel mileage drop from 15 mpg to 9. That's a 60 mile loss with 10 gal of fuel.
RAM at least had a 3.4 and my drop was only 2mpg. (15.5 -13).

 

[Jonnerns]

Does your transmission now shift as you want when going off the throttle or is it still "hanging" in gears?

 

[ms14796]

Does your transmission now shift as you want when going off the throttle or is it still "hanging" in gears?

Yes...let my foot off throttle and there's a delay. RAM would upshift as soon as I eased off throttle.