Eventually I will change my rear diff, How difficult or expensive will changeing an 09 3:55 to a 3:92

 

x2 but 3.92 to 4.10 on an 03

 

If you have never done any gear work, stay away from it and pay a pro. It is hard to set the gears up correctly, and you could end up causing much damage!

Zack

 

As said above.
You need specialist tools and a LOT of knowledge and especially experience, to set up a diff.
If you don't have both of these, don't try it!

 

similar question: how hard is it to just put in a rear LSD? Like, if I just wanted to add an Auburn or DTT to my current open 3.92?

and on switching to 3.92, you're better off just buying an axle and replacing that since 3.92 are a common gear set.

 

if you have to ask, then you better find a good shop to do it! If you don't know how to do gears, you can screw them up easily! And it is spendy, but the best Mod I have done yet! But don't waste your time going from 3.55 to 3.92. You won't hardly notice a difference! At the very least go with 4.10 and better yet go with 4:56. You won't regret it! And if you get the gears done, you can normally talk them into installing a LSD like the auburn, or the detroit tru trac for next to nothing! For gears and a Detroit Tru Trac LSD it cost me Approx $1800. I can't remember the exact price!

 

physically putting the gears in bolting it up is easy. the hard part is getting all the tolerances and clearances inside the casing and between the pinion and ring to fit perfectly. tools that are uberexpensive that most ppl don't have... gear swaps are for the professional shops.