I took my rear diff apart so I can re-assemble the plates correctly--the way the service manual says. Upon taking it apart, it seems I've had a leak at the top of the diff for a while. There's black gunk all over it. Is this because it's got a bad gasket seal from factory? It's never been worked on before. Do I just need to make sure I do create a good gasket with RTV when I reassemble it?

 

Is it a tar like gunk? If so maybe its just the underbody rust proof coating.

 

Maybe. I'm not a very experienced mechanic to know how to tell the difference. It appears to be something oily with a lot of sand/grit accumulated.

 

The problem will be fixed as soon as you re-assemble it. There is no gasket it's all RTV.

 

I'm not as verbose as sir D. Buschur but it has been talked about by at least one of the "******s on EVOm " https://www.evolutionm.net/forums/6214595-post8.html