2020 Sierra 1500 6.2L shudder....

[shadysneed]

Hello all, within the past 3-4 months, my 2020 Sierra 6.2L has started to shudder between 1,100 - 1,300 rpm while cruising 40-50 mph range. Truck just broke 11,500 miles. I'm really starting to think it's DFM related. If I catch it in the act, I usually give the truck a little gas and it corrects itself. The shudder literally only happens in this rpm and mph range. Dealer didn't have much to say involving a fix. Shocker....

[Grumpy Bear]

36 minutes ago, shadysneed said:

Hello all, within the past 3-4 months, my 2020 Sierra 6.2L has started to shudder between 1,100 - 1,300 rpm while cruising 40-50 mph range. Truck just broke 11,500 miles. I'm really starting to think it's DFM related. If I catch it in the act, I usually give the truck a little gas and it corrects itself. The shudder literally only happens in this rpm and mph range. Dealer didn't have much to say involving a fix. Shocker....

DFM/AFM tend to fight the convert lockup tables in this range under light loads at these speeds. The DFM can have any number of cylinders 'working' and in some of those modes it's like a lawnmower motor pushing a 6K pound truck. It struggles with having enough power in that mode to provide that load. So it switches modes. If it does that as the converter locks or unlocks....burrrrrrrrrrrrrrrrrrrrrrrrr  

[OnTheReel]

Grump is right. DFM. Mine does it too. But for the purpose of elimination...run it (from a stop) in L9 up to the affected speed, and see if the issue persists.
 

Reasoning is, DFM is not active in “low” mode. And the trans would never be in 10th gear at 40 anyway. So the only difference in L9 vs drive at those speeds is going to be DFM inactive vs DFM active. 

[Sam321]

I have a question about this.  I can put my truck ( a 6.2 10 speed) in low mode (L) and select 10th gear.  Will DFM still be inactive with 10th selected because I am in L?