Sorry everyone. I know this is an older thread but I have been searching for weeks and came across this today which almost describes my situation perfectly. Looooong time reader (5 years or more) but I have never joined up until today.
But I was hoping for some insight from anyone on this post or familiar with this issue.
I have a 2021 2500HD 6.6 gas. I pull a fifth wheel of around 11,500 lbs. My issue is when I am accelerating while towing I start getting a jerking/misfire "fishbite" feel starting around 3000 rpm up to about 4000 rpm. This started at about 12,000 miles on the truck. It mainly happens in 3rd gear between 3200 rpm and 3800rpm but has started doing it in the end of 2nd gear and even 4th occasionally.
I brought the truck to the dealer with the trailer attached and the tech rode with me. He felt it as well. He brought along a laptop that was connected to my truck. He recorded some snap shots of all the data while it was doing it. The data was submitted to GM and they noted that the slip speed was more than tolerances allotted. They recommended replacing the torque converted and inspecting the trans pump. My pump had a few cracks so he replaced the pump rotor and torque converter. I was hoping for it to be over. However once I hooked to my trailer again, it was still there. Just as bad as before. We did another test drive and recorded the data again but he and another tech seem to be at a loss as to what is going on.
Just FYI it does it with or without tow/haul engaged, cruise on or off, air conditioning on or off, stabilitrac on or off... none of it matters. I have even pulled it without the trailer plugged into the electrical to eliminate any trailer brake malfunctions... It happens around the same RPM every single time. I have pulled 4 other trailers the heaviest of them weighing about 7000lbs all bumper pull. No issues present on any of them.
I am waiting to hear back from the dealership still but looking for answers on my own