Adding 600 lbs to the rear of the 3500 will reduce the pin weight about 400 lbs depending on the distance from the added weight to the center of rear axles and distance from the hitch pin to the center of the rear axles. If the distance is equal, then 600 lbs on the rear will reduce the hitch pin by equal amount of 600 lbs. Most likely the difference is 60% of GVW in front of axle center to 40% of GVW rear of axle center. I would strongly suggest to hit the CAT Scales and weight the rig to ensure proper weight distribution and not overloading the rig.
Forrest
