how hard is this to do and how long does it take?does it require a mechanic(or can i do it in my garage)?what differences will i notice if i swap my 8in limited slip to a 9in limited slip.?ie will i gain horsepower?
If your talking about just swapping the axle's out (the 8 for the 9) and you get one that's a bolt in application, it really isn't all that hard. If you have the space, tools, time, and some help yes you can do the swap in your garage.
Basically, support both the car and the axle with jack stands, unbolt the leaf spring plates/shocks/u bolts/etc and now it's prepped for the swap. From there you have two choices - 1. With the help of a friend you can lift the axle out and over the leaf springs and pull it out, thereby leaving the leaf springs in. I don't suggest that because it's heavy and a huge pain to do it that way.
Or 2. Since you've got the axle supported, unbolt the rear leaf spring shackles, drop them down, and roll out the axle with the help of a jack to guide it, supported by the pumpkin (and to give you something to roll it around on once it's out). Installation is the reverse - support it with a jack, raise it up, and bolt the rear shackles back up before lowering the weight of the axle back on the springs. This is the way my friend and I did my axle swap. In and out in about an hour and a half.
If you gut the rear out, now would also be a keen time to replace anything you want while it's out. Benefits of the 8 to 9 swap? A good rear end to hold up to performance applications.
You will not get more hp in swapping. If you have the same gear ratio, you won't notice a difference at all. The difference is that the 9" can handle more hp, and the racers really like them because it is so easy to swap the gears out. If you aren't getting over 400hp or more, you aren't doing it would kind of be pointless to do, but it's easy.
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