i just regeared.. so my question is which oil do i use and should i put any additives?? the garage guy said to put dealership oil and limitedslip additive? i have dana 30 front and dana 44 back, first time im regearing so i have no clue.... any input guys???

 

manufacturers recommendations are for the axles which are the same (D44 and D30) not the gears inside. So that makes sense to go with spec to me.....If you still have the LSD function after re-gearing then use the additive. If not, don't.
IMO.

 

dont all jk's have limited slip in rear diff??

 

nope. most are open and rubicons have lockers. if you use a good synth gear oil, you don't need to add friction modifier as it will already have it in it. i like to use royal purple or mobil 1

 

mobil 1 sounds good... ill get some tomorrow, any specific weight?

 

i use 75W90 as is recommended. if you do any towing, you will want to use the heavier 140 stuff

 

no towing at all, so should i use it as my break in oil? or should i use normal oil and then after 500 miles put the synthetic?

 

you can use regular gear oil during break in and then change it out for the good stuff afterwards

 

This is what I would do if it were mine:
Use regular oil (with additive if Limited slip) for the first 1500 miles or so.
Drive the first 10 miles conservatively and stop to let the differential cool down. Accelerate and decelerate easily a few times during this 10 mile ride.
Do this a few times, letting it cool between times.
At around 1500 miles, drain the oil and refill with synthetic.
Not letting it get too hot at first is crucial to long life.
If all is well, you will notice lots of very fine metal in the oil when you drain it at 1500 miles. This is normal from the gears lapping in.

Most people just start driving from day one, never change their diff oil, and get long life out of their axles.

Being careful as stated above is considered overkill by many.
The choice is yours.

 

ronjenx gives good advice.

I just swapped out my diff covers for riddlers and I was really quite surprised at how black the diff oil was. This was with under 4000 miles on them!

Synthetic is the way to go as it essentially never breaks down.

I'm gonna change the transfer case fluid next.