So I wanna get rid of the 1 wheel peel in the truck with a posi unit. I'm gonna keep the same gear just change out the spool. Can I simply remove the center section and swap the open spool for a posi unit and reinstall with all the same caps and shims on either side? Or will the posi unit be bigger or smaller requiring me to reshim the gear?

 

In a way, yes you can. But you need to check the back lash before you remove the center section. Make sure it matches when you install the ring gear on the new center and adjust if needed.

 

I took the locker out of mine and put a truetrac in. Backlash before and after measured close enough to be "the same" with the new carrier, new bearings, and original shims in the same place. No issues at all. Not saying you shouldn't check it, but I think you'll probably find it's OK when you do check it.