Just changed from 321's to 488's. Due to cost my rear is now open, was LSD with the 321's. What kind of performance difference should I expect. Also was recommend to install a lunch box locker, not sure what this us.

 

The "brake-lock-differential" that all JKs have will kick in much like the limited slip did.
It won't be quite as seamless, though. But, it's a pretty good feature.

edit to add:
The BLD works on both axles when in 4wd.

 

Mine has gotten me everywhere I have wanted to go with the brake lock feature. I have been tossing up the idea for a locker but I was gonna throw it in the front not rear and the lunchbox lockers its just one that goes inside your existing carrier usually they take 3 rotations to engage but work everytime you don't have to worry about air lines or cables breaking

 

Does it I've only noticed it in the rear

Edit: I've had it at some pretty weird situations and the usually one of my front tires just spin I can usually feel the back when it starts to spin bc it hops for a sec then catches and walks up whatever I'm climbing up

 

As per the manual, BLD works on any driven axle, I.E., if you're in 4WD, it should work in the front, too. I've actually seen it working on the front of a buddy's JK as he was coming up a nasty hill.

 

BLD + Truetracs!!!

 

Wait? What cost? It shouldn't cost anything extra LSD or open? They are not replacing anything extra back there. Unless I seriously missed something....

 

3.21 to 4.88 is usually a carrier change. Not sure if the original LSD stuff would fit in the new carrier, but I'm assuming not based on the fact that his weren't re-used.

Lunchbox lockers, also called auto lockers, are always on when the axle is being driven. So an auto locker in the rear pretty much means the rear is always locked.
In the front, you'll only be locked when in 4x4. Otherwise they are practically invisible.
I ran an Aussie locker in my front diff in my '07 2-door, in 4x4, it made a HUGE change in how easily I ran through stuff. The Jeep seemed to crawl its way out of everything. I was also still running the open diff in the rear, and was planning on putting a selectable locker in the rear diff, but then I traded my '07 2-door for an '11 4-door Rubi.

 

Rear carriers do not need changed on JK D44 gear changes. Don't know how the OP lost his limited slip

 

That's what I thought! I even posted a thread and was told it would be unaffected... Had me nervous for a second, my gears are going in monday