Volvo I-Shift low rpm 10,11,12 gear problem NO CODES see video

How would someone check this exactly? I measured mine on both sides from ground to bottom of 5th wheel (where 5th wheel slides" is 40". I was loaded though when I checked it. My psi in my bags is between 4 and 7 when I'm bobtail and 12psi when I have an empty trailer. I have a '13 volvo 780.i get this bounce and engine sounds like it's chugging along especially going uphill. The bounce almost feels like the tires are losing traction. But no real fluctuation in rpms, other than the maybe 25 rpm tick I notice when it does it.