i just removed this differential and wnated to know if it is an open ended or lsd...? is there any way to find out which it is... the person who had it before me said it is lsd

 

S4 or S5?
The following should be for s4 open or clutch type. Ive popped open a viscous before but dont recall how it looks.
Drain it.
pop one of the axel stubs off and look inside.
Then rotate the pinion flange.
If its an open differential, you should see a what looks like a round bar spinning inside.( like a baton being thrown into the air)
If its an lsd, you should see a flat surface with an indentation in the center.
Check the S4 FSM chap 9 page 29-20 to see how different the guts look like between the two

If you still cant make it out, pop out the other axel stub and remove the rear cover. If you can see inside the center chunk casing, its an open. if its sealed, its a lsd.

 

easiest way to tell if its lsd or not: Spin the axles. If both sides rotate in the same direction its an LSD, if they spin oppositely then its open dif. Another way to tell is to look at the fill plug, most of the time an LSD unit will have a metal plate that says to use limited slip fluid. sometimes this plate is discarded or ripped off over the course of a cars lifetime so the easiest thing to do is what ive already suggested.

 

What kind of LSD does a s5 have?

 

s5 has viscous....which sucks because the fluid in it is so freaking old that it will probably overheat first before it even locks....