Both methods are acceptable. Being a weenie, I do both. I keep a couple extra 8.8" Felpro gaskets on hand for when the time comes (five bucks or so each). I use Copper and the gasket.
But some just use RTV and some just use a gasket (the former is better than the latter, if choosing just one, IMHO).
It is kinda like t-stat housings - some guys RTV and some use a gasket and some (me, once again) do both.
Both methods are acceptable. Being a weenie, I do both. I keep a couple extra 8.8" Felpro gaskets on hand for when the time comes (five bucks or so each). I use Copper and the gasket.
But some just use RTV and some just use a gasket (the former is better than the latter, if choosing just one, IMHO).
It is kinda like t-stat housings - some guys RTV and some use a gasket and some (me, once again) do both.
I run Royal Purple in the Mach 1 and dino in the 93 cause I am too lazy to change it out.
I just use RTV for the rear cover. That is what Ford uses from the factory on the 8.8s now. When I changed the diff fluid in the Mach 1 I went to Ford to get a gasket and was informed that they don't have any and they just use RTV and sure enough when I pulled the cover off, no gasket just RTV.