Diff lowering kit I was supposed the first installation of the second generation differential lowering kit. I can not tell you if it has made a difference in my vehicle. The drop is in the neighborhood of .5 inches. Do most people with a lift utilize this, probably not. Have I heard of a lot of people destroying half shafts without it, no.
[edit] - The extra droop is an issue as noted by aero steve in a reply below.
Binding of the CV's has been heard from my vehicle, but then again, we were trying to get our trucks off the ground.
Hang Time Check some of the MANY threads on the shocks.
Happy decision making.
Todd