I will be having a shop install gears for me in the next couple weeks.
Should I also get some friction modifier and premium gear oil? Or is regular gear oil with out friction modifier good enough?

I will have to check and see if the shop even allows other fluids because some will only use theirs.

 

I don't think it would hurt to get the friction modifier, the shop that installed my gears put some in to see if it would stop the whine. It did'nt so there working on my car as I type.

 

its not for gear whine its to let the posi slip more around corners. Its ok to not use it if your posi is old and worn cause then it will bit harder since its allready worn, sounds redneck but its an ok way to make it last a bit longer.