Changing differential fluid and cover gasket 14 bolt. questions

[z71HalfTon]

Hey guys the cover on my 14 bolt is seeping so I have decided to replace the seals and gear oil. Can I use a gasket instead of rtv or whatever gasket maker is previously on it? And what weight gear oil should I use? Thanks!

 

[GoToGuy]

Gasket or RTV approved for diff cover. What does FSM recommend for your diff's lube? Most are 85-90.

 

[454cid]

80w90 or 75w90 synthetic. GM switched to synthetic in 99. Either should work.

No LSD additive if you have a g80, and won't matter in an open diff.

I like gaskets. My 14bff used a gasket from the factory and I've used original gaskets when I e changed the oil.