Does the friction modifier additive for limited slip diff make the oil darker than normal?

 

Not that I've ever seen. Then again, I've always used the bottles that came with the additive in it already.

 

It shouldn't. Is this the limited slip or posi rear end? The gm additive is only needed if you have the posi. I asked the dealer about it recently since I'm going to be changing the diff oil soon.

 

Only if the additive is noticeably darker than the oil, given the proportions of oil to additive. Why do you ask?
By the way, limited slip & Posi are the same thing. Limited slip is the function of the differential, Positraction is just GM's "proper name" for limited slip. Other car manufacturers have their own name they give to limited slip.

 

I only ask because I recently replaced my rear end with one from a junkyard, and I needed to install an actual gasket because the shop used sealant to make a gasket...and it leaked 😡. There was only a few thousand miles on the oil and it was pretty dark.