Looks like all that grease has been doing is collecting dust and mud. Those are badly neglected and it looks like in this picture that the upper bushing has been worn completely through. It's possible the lower spring bushing has also. You need a complete shackle kit, which includes threaded bushings that you'll need to press into the springs and shackle mount. You might entertain replacing that upper mount also (with a used one from another 'bolter,) as that cavity worn thru won't support the new bushing properly. Maybe a welder can restore it and redrill the hole for the bushing. The bushings on the springs on my truck were so bad that I elected to just replace all 4 springs. You might wind up doing the same.
The usual vendors carry shackle kits to replace the whole thing.
HERE'S ONE OPTION for 1/2 ton trucks.
[on edit] You should add a signature to your profile that has info on your truck so we don't have to guess what you're working on. Click on your username at the top right and choose "edit profile" in the dropdown menu.
