These rear shackles actually lower the rear - (sorry for sounding like a dum a$$) but I have seen the picture of them installed and for the life of me can't see how installing a longer larger shackle in that location actually lowers the vehicle - one would think it would jack it up farther... I am confused

So can one of you experts chime in an edumacate me... dah....

 

Look at that picture and think of what would happen with no shackle at all. The springs would go all the way up to the bed of the truck allowing the truck to lower towards the axle.

The reason a longer shackle works to lower the vehicle is due to the frame mount for the shackle being "below" the spring. Now if you put a 2" longer shackle in, it allows the spring 2" closer to the truck, allowing the truck to set closer to the axle.

Keep in mind, the axle is not going anywhere, its height is dictated by the tires touching the ground.