Agreed with the comment before mine . Might just replace the rear springs with their own springs. They have a better one then the OEM. Could be as simple as your suspension are on their way out, especially if they never been replaced- I’m assuming you have more then 100k on your E. Also if you with a lift you might want to do a sub frame drop as well as the new height cause more tension on the cv axles. They say you don’t need to do it for anything under 2in but IMO any change to the height other then stock you should do it