Therealnpp

Correct. But they only replaced the valve body after the ECM didn’t do the trick. I was told by the service advisor that GM contacted them and told them to replace the valve body.

I don’t recall the TSB number but the ECM never fixed the problem. They ended up replacing the transmission valve body per GM and that did fix it.

Correct. But they only replaced the valve body after the ECM didn’t do the trick. I was told by the service advisor that GM contacted them and told them to replace the valve body.

The dealer replaced the valve body in the transmission. I’ve got 5100 miles on it now and it has been great ever since.

Aside from this shudder, I love everything about the truck. Hopefully they can fix it, whatever it ends up being. Thanks again

In regards to the DFM and different modes, I'm aware. What I am saying is the speed and time at which it shudders changes. The shudder is exact at certain moments when the DFM is functioning but the shudder moves to different speeds based in the mode I'm in because the transmission shifts are now different. The DFM in these trucks is pulse width modulated through the use of the torgue converter. My initial thought was the TC was locking up at slow speeds, but according to the technician, the transmission was working the way it should. He effectively noted that the shudder was happening at the same time the DFM was activating. Yes, I'm skeptical of the ECM because they rarely fix anything, but they have in the past. So, we'll see. It's at least a starting point. But based on the number of views this post has had, it doesn't appear that there are many people who are having similar experiences, which leads me to believe it can be fixed. There is also a TSB out for exactly what I am experiencing. I also want to add that the torque put out through a diesel will be vastly different than a gas engine. My concern is very specifically occuring right at 27mph when I am not on the throttle and just barely tip back into the throttle. Which also leads me to believe that the truck is in DFM mode and is not properly coming out of DFM mode. I appreciate your feedback, though. Thank you for taking the time to respond.

The dealer confirmed it was DFM. It's there now and I never checked 4-high. The shudder changes in sport mode and trailering mode. Which leads me to believe (as well as the tech at the dealer) that the DFM is activating when it shouldn't be. We'll see what happens. It doesnt shudder under high load. It shudders with next to no load. It's def not the Ujoints.

Just wondering if anyone else has had this problem. I have a 2020 TB LT with the 5.3 and 10 speed and I keep getting a really bad shudder at low speeds. Specifically 27-40mph (sometimes higher) when I'm steady state driving and just begin to tip into the throttle. It's at the dealer now and they have confirmed and are firing an ECM at it, but I'm always skeptical about ECM "fixes" Hoping other people can chime in with similar problems or no problems. I'm hoping this isn't just poor design and something can actually be fixed.