I am getting my housing back fixed in the next 2 days. The center section I have is a cast iron case with ford 3.70:1 gears, it is a Detroit light weight locker. I had the center section professionally setup 3 yrs ago and it has been keep sealed in a storage case. I took it out to look at it all still looks brand new as it should since it all is except the gears. My main question is what gear lube do most prefer to run with a locker like this? Detroit said the recommend synthetic gear lube. but did not give me specific weight of oil, they did say that is determined by the climate you live in and use. They did say posi additive was not needed. So I am asking what to use here hopping to get some good answers.