I bought a rearend yesterday and he said he would reccomend replacing the 2 bushing, they are near the differential... What are they for and how much and where can i get them???
I believe the bushings you are talking about are the upper control arm bushings.
If they look cracked and beat up, they should be replaced. Prothane makes replacement kits. For about $60 you can get a complete set of urethane upper and lower control arm bushings for your rear axle. You just need to know if the upper control arms have the oval, or the round bushings where they bolt to the frame (just stick your head under the car and look).
The old bushings can be a ****** to get out of the metal "bushing shells", which you will need to re-use. I've heard burning them out is one way to remove them, but it sounds pretty dangerous to me. I just drilled out the old rubber all the way around the bushings until I could pry them out with a screwdriver. It took a long time.
Using fire to remove bushing? How caveman! Maximum Motorsports has a tool to remove those bushings as well as the bushings by themselves (no need to buy a whole kit to get 2 bushings). Summit also sells just the rear bushings.
There is a little known fact about rear upper trailing arm bushings that most people don't know: A rubber bushing needs to be left in one end of each rear upper control arm because if it isn't, binding will occur in the suspension travel and two things can happen: poor traction (straight line and cornering) or the ears on the housing can break.
Now, that said, getting the bushings out of the housing is pretty simple with the right tools...Ford sells them, but they are ridiculously expensive. Basically, you need to create a cup (I used a large diameter pipe with a huge washer on the end) that will fit around the bushing and still evenly contact the housing ear. Then utilizing another washer (the same size as the diameter of the bushing shell), run a bolt through the "cup" and the washer on the opposite end with a nut and just tighten the bolt and nut until the bushing pops out. You may have to drive it the rest of the way with a hammer, but be careful not to hit the housing ear. Before you drive the bushing out, measure the relationship of the outer shell lip to the housing ear with an inside caliper and repostion the new one by turning your "cup" tool around the opposite way and pulling the new one in...a little oil on the bushing shell will help some.
I personally find it easier to leave the bushing in the housing rubber and changing the one that connects to the body to polyurethane or aluminum (as in the case of the Global West/Ford Racing Del Alum bushings).