If you have no pinion angle, then you have no axles in your truck. If that is the case, you have bigger issues than a shudder. :rof
The pinion angle is the angle between the differential and the driveshaft. If you take a truck in for a driveline shudder, the tech is going to measure that angle. Then they will determine the correct size wedge to install to rotate the axle to adjust that angle. To do that on my Jeep, I just adjust the control arm lengths. :$:
The reason you experience a different shudder with different loads is because as the suspension sags under the increased weight, the pinion angle changes. If you have a good tech, they can adjust the angle to be correct under full load, some load, or no load depending on how you use your truck. They just need to add weight to the truck to get the suspension to squat to your normal load level, then measure and adjust at that weight.