so i have a limited slpi or posi whatever you want to call it, sitting in my garage and i want to swap it for my open diff, my question is im not going to change the gear set so do i have to set backlash and all that to just change the diff? if i have to then ill change the gear set i have 2.73 currently and a set of 3.42 on the posi unit.

 

if all you swap is the ring gear all you have to set is back lash if you swap gears you ahve to set the pinion depth, preload, plus back lash.

 

If your posi is a 3 series, which it most likely is since it has a 3.42 ring gear on it, then it CANNOT POSSIBLY be used with a 2 series gear set.

In other words, you would have NO CHOICE but to change the gears as well, in order to use it.

Find out if it's a regular ring gear, or the "special" thick kind of 3 series gear to mount on a 2 series carrier. If it's the "special" one, then the carrier is a 2 series, and you can use it. Otherwise, if it's a GM gear or something, then it's a 3 series carrier, and there's no possible way to make it work with 2 series gears.