2024 Allison transmission vibrating

[James Z]

I just purchased a '24 2500 Duramax and have about 1400 miles on it. I towed a cargo trailer yesterday(about 5500 lbs but a tall trailer) and while the truck pulled well I was disappointed in 2 things.

1. There is a noticeable vibration/shudder at around 1200 RPM when under load. Anyone else experience anything like that?

2. Also, I had gotten 19+MPH on the trip in to get the trailer but got around 9MPH coming back. That seems pretty low although I did have a stiff head/quarter wind for a good while.

Just curious if anyone has any thoughts.

Thanks!

[redwngr]

How tall/wide and how heavy was the trailer? 

Flat or upgrade one way and downgrade the other?

 

Aero load matters, more than many expect. 

I get that sometimes we need to run with traffic, speed increases area load, especially with a trailer.

 

The 25mpg fuel economy info page gives last 25, best 25 and instantaneous mpg.

Watching it can show impact of wind, driving speeds, running with traffic (drafting) vs running alone, trailer etc.

[James Z]

Trailer is over 7 ft wide and about 9 ft high. 5500 lbs. Definitely more upgrade on the towing portion than the empty. I don't think my truck has the instantaneous mpg page. I have a Silverado LT