Is it normal for the frame of a truck to flex when going up steep hills at an angle?

I was driving my 94 Dodge Dakota up a steep driveway at an angle (the left wheel hit the hill first) and I noticed the bed jutting out a good inch or 1/2 inch as the back wheels came toward the hill. As soon as I straightened the truck out it was gone. Is it normal for the frame to flex or bend like that? I had never seen that happen before and it scared me shitless