Original poster here.
The truck is a 2000 Chevy 1500. Trailer is 26' 5500# 650# hitch weight. The hitch was installed 6 years ago and we towed a smaller light trailer for a few years. We have had the current trailer for just over a year and have towed about 5000 miles before the failure. The dealer that installed it is in another state and I won't pursue any help from them.
The current mechanic who does a lot of hitch work and custom fabrication said the hitch was not designed for the truck and the installation was "wrong" because it was not the correct hitch.
The rear mounting bolts were drilled through the frame member in between two factory access holes to get to bed attachment bolts. The area between these access holes was only 1.5" so there was very little metal to support all the weight. after a 1/2" hole was drilled to mount the hitch. That is the place it failed it deformed the frame member there. It did not pull out but if we would have tried to drive after the WD failed I think there could have been a complete failure.
The frame repair will be minimal and a new hitch designed to my truck will be installed.
I never inspected the way the hitch was installed originally but I will be watching how the repair and installation of the new hitch goes.
I guess there really isn't a moral to this story I am just thankful that there wasn't any more damage it could have been a disaster!
jesseannie