information needed on 4-6'' lifts

I am wanting to throw a 4 or 6 inch lift on my truck. i hav 33'' tires and 18'' fuel boosts waiting in the garage. i am looking at BDS lifts. i want just the basic lift, cant afford the coilover lift. Any pointers before i go with the lift? will i hav to worry about correct drive shaft angles? will anything wearout due to the lift and how can i prevent it. different gears in the rear? also hav a wierd thump in my rear end, over wash boards and little bumps, sound is worse in cold weather, anyone else?. thx everyone!