Class C rear end sag and banging!

The problem with buying/using/replacing your springs with "used springs" is that they fatigue over time. For the most part, IMO, you have no way of knowing the condition of used springs without trying them out on your rig. (unless you KNOW the condition for sure) Class C E350's are real tough on springs because they are almost always overloaded or close to it. Age is another factor. Adding "helper" springs to already worn springs may be of little long term help but that's your choice. There's nothing like the ride of a new vehicle which usually comes from replacing ALL the worn suspension/steering parts. IMO, making the suspension "too stiff" is something you'll probably regret later. You all ready know what it's like when it's too soft.

Chum lee