i've had problems with these since the first install. when i first put them on, the nipple that aligned the axle broke off and i had to drill all the way through and put a long center pin through. since i've had them, the ride got gradually worse and worse.
finally, it got to the point that the truck vibrated terribly in every gear and i finally decided to throw it on the lift at work and check it out... turns out BOTH blocks had giant chunks missing letting the axle tilt backwards and making the u-joint bind slightly. never again will i buy blocks from DJM.
i replaced them with the 'superior automotive' brand that autozone and oreilly carries and they're a ton better. much better and more solid material, not shitty cast.
if you're using these lowering blocks, i suggest keeping an eye on them.
edit: picture was taken during removal, btw. i'm not running just one leaf spring lol