Most (99.99%) gear lubes already contain a friction modifier. It's very hard to find one that doesn't, but you can know for sure if it has the additive if it says something like "compatible with limited slip differentials" on the back label.
The exact viscosity of gear lube for our axles is not as important as it is in our engines. There's actually very little difference between them. An 80W-90 is fine, so is a 75W-90... as is a 75W-140. Basically, steer towards lower viscosity numbers for cooler climates, higher numbers for hotter climates or if you tow a trailer.
Brand-wise, pretty much any major brand will be fine so long as it is a GL-5 which is the type of gear lube our axles require. I use Valvoline but I wouldn't turn down any of the major brands.