no one ever seems to know to use angled blocks, shims or cutting the drive shaft. every truck seems to be different. i've heard that if you going lower then 3 inches you'll need some type of angle or shim. the other thing, people may too shim their carrier bearing. bell tech couldn't give me a straight answer on weather i should use a block that was angled or flat. in my case my drive shaft was cut (i lowered myself and had that done) i did not have any vibration and i dropped mine with a 2inch angled block and 3 inch drop leafs. the rear sat lower then the 5 inches i thought, maybe because the leafs are for a regular cab. i would recomend measuring your pinion angle to be safe.