Backfire/miss when shifting no codes

[nkoch123]

I got a 2021 2500 Tradesman 6.4 with the 8 speed. Bought it new in 2021. With the tow/haul on, when the truck shifts from 1st-2nd and 2nd-3rd there is a backfire or miss. Now when the truck is cold it does not do it. Shifts perfect. But when I drive it then park it for a little then drive it it does it most of the time. There are times it's fine. It seems to be worse with a load. The other day it did it between 3rd-4th for the first time. When tow/haul is off it only does it between 1st-2nd. I have had it back to the dealership a couple times, there are no codes and didn't do it for them. Any ideas? I'm at a loss. I love the truck but this is annoying.

 

[ZF.Transmission.Guy]

During a shift, the transmission requests a torque reduction. Every modern transmission does this.

The engine will first try to meet this lower torque request by changing spark timing, then adjusting fuel if the torque reduction can't be met with spark alone adjustment alone. Typically, the transmission tries to keep the torque reduction such that only spark adjustment is needed.

My first guess is something spark related(plugs, coils, wires). When is the last time they were done? It may be worth a shot to take a look at the condition of the spark plugs.

If all of that looks fine, my next guess would be air or fuel control or delivery. I'm not sure where to start with that one, I'm just the transmission guy.

 

[nkoch123]

I haven't checked them yet. I was planning on changing that this year. I am just over 50k miles. It has done it since I bought it. But I will definitely check the plugs here soon. Thanks for the explanation