differential oil question
 

I want to change the oil in my rear differential,do I need to add any thing to the oil for the limited slip? I'm using mobil 1 full synth 75-90 gl5 rated oil.

No

please get your facts right before posting..

for the poster: let us know what kind of car you have and if it has a stock rear end. getting tired of trying to read minds... if it has a limited slip clutch S4 differential then you need limited slip additive from mazda or equivalent from another source or your clutches won't last long without it.

86 na base model stock rear end

then you don't need any special additive, the oil you have should work fine.

You don't have limited slip.

But yes people with the clutch type LSD, like Karack said, need a differential additive. I've used Redline and GM additives and they're both great.

I am geting ready to do the same thing. I have a 87 GXL with auto trans. What oil is recomended and do I need addatives?

You'll only need the additive if the rearend chatters after the fluid change.
I use Mobil1 gl5 75w90 and it works great. No need for additives since it already has some in it.