I dont think you hurt anything by doing this or wrecked anything.The battery will suffer the most damage when you use the starter to move the truck. This is an age old practise and all you are doing is using the starter motor as a winch,which was not designed for the load you put on it. I would not suggest you do this very often and certainly not for extended lengths of time,a few seconds intervals will allow the starter windings to cool.Dont drain your battery because that will destroy it.
Hobert
