Why does my truck shake and jerk when I slowly back up?

What is your question?

Jerking and shaking seem to only occur when I slowly back up. At higher speeds the shaking is only slight. This has gotten worst over the last few months. At first it was barely noticeable, but seems to be getting worse day by day. I have 310,000 miles on the truck and have mostly just had repairs that should be expected for a truck thats 23 yrs old.