I finally got off my rear to find the manufacturer of the ball mount that I have been using. I really feel this product is doing a good job in saving my differential and I thought I would pass this information on. This unit has rubber dampers internally which help control the lurching from bumpy roads and the sudden jolt on the differential and drivetrain when accelerating or braking.
You can see a metal insert that sits inside of the ball mount where the hitch pin goes through. On each end of this insert are the rubber dampers. For the $70 or so, I would suggest giving this product a try as I have about 3000 miles on this product.
The manufacturer is Convert-A-Ball and the product is their "Cushioned Ball Mounts" available in 2' drop increments. Rating shows max trailer weight of 10,000 lbs, max tongue weight of 2000 lbs.
http://www.convertaball.com/ballmounts.htm
p.s. I am currently using the AM-SC-4 but considering the AM-SC-2 (4" vs 2" drop)