At what point are diff drop and carrier bearing kits necessary?

I have 5100 at the top setting and considering rear shackles.

 

I have 5100's at top setting and Toytec shackles at 1.5 and I added a drop due to just wanting my drive line aligned with little to no angle. I did it very simple with SS washers and longer bolts. Easy

 

To answer your question correctly = if you have the shakes then do the drop.

 

Looks like the +3 shackles include the carrier bearing kit. Do the diff drop as well?

 

Sorry, it looks like I said shackles, but I meant shakes / shaking when you are driving due to a bad drive line angle.

 

Shackles change your pinion angle from stock - there is no aligning that as long as the shackles are installed. If you are concerned about angles then blocks are the way to go.

 

The carrier bearing drop kit is like $30 and two minutes to install, its cheap and easy enough to just drop it regardless of if there is a noise or not.

 

I have 5100's at the middle setting with a front diff drop. Truck had a 3" kit when I bought it so it was on there already. With 1.5" lift up front I have little to no cv angle which I like. Took the block off the rear so I did not do a carrier bearing drop.

 

I had to do the carrier bearing drop with a 2 inch block in the rear.