on the rear "axle hump" of the frame there is a bumpstop, with a steel plate and (I think) one 1/2inch bolt that holds it on.
Ive seen 3 different trucks where they hold moisture and rot, when they do they will bore a hole right throught the frame...so take a look at your truck!
I didnt get a picture of the crack on my frame... but the hole had spread to a crack about 1 inch long going vertically up the frame...

mine is the 3rd truck I have fixed now, one was a very nice "rust free" 93, and it was a big gaping rust hole under the bumpstop
i put a piece of angle iron in, welded it up, called it good. i know its not good to weld perpendicular o the length of the frame...but it had to be done

