I have an 11 crew cab 2500 g56. when i pull heavy goosenecks or fifth wheel camper i get what feels like axle wrap. on take offs or hitting bumps going down the road. when i pull bumper hitch i get no problems.
gooseneck generally weighs full loaded 14k. bumper hitch weigh 16k. what would be best weigh to stop the problem?

 

Even though the goose weighs less than the bumper pull it has more pin weight ie more on the truck suspension. so the goose is changing the drive line angle more. an option would be traction bars that would help keep pinion angle from changing as much. They come with their own set of pros and cons and you would have to decide if it is worth it for your needs.

If you do some seat of the pants testing you may find that certain speeds/rpms in certain gears makes it better or worse and if so then you could cut it by driving around it ie (totally made up numbers) you feel it in 4th gear at 2000 rpms and 40mph but not in 3rd gear at 2300 rpms and 40mph and knowing that when you need to drive 40 make sure and be in 3rd gear instead of 4th. I would suspect that when you feel it is more upon acceleration/higher torque loads than just cruising.as the rear axle is twisting downward creating more angle

On my 01 I would have the issue driving around empty so my correction was to lower the center carrier bearing with a spacer (for my truck and how it was 3/4 inch worked) to decrease the angle and it worked great but since yours appears to be only when loaded somewhat heavy dont know if if that would help or not might make it worse might be worth a try though it is cheap. OEM drive line angles only work within so much range. You fix the high end of the range you might feel it on the low end or vice verse

BTW I am no drive line expert by any means

 

I got looking and i have a one piece drive shaft so no carrier bearing.guess i need to put a load on the back of truck and see what the angle is compared to empty.