For a 2 wheel drive, 2004 f150. One site says you need a gasket, the deal says you don't need a gasket just the silicon gasket maker. Who is right?

 

Just did mine. 2006 no gasket. Used black silicone if I remember right. Got it very clean and sprayed with brake cleaner to dry it off. Followed directions on the tube and got very good results. I did wait 24 hours before putting fluid back in the diff.

 

I'm sure someone still makes gaskets for the rear end, but RTV is all you need. Heck, they don't use gaskets on the assembly line for this seal.

FWIW, if you've got a limited slip diff, be sure to add the friction modifier. Pick it up at the dealer and put it in first. It's just easier to put it in first, so you don't have to figure out how to get some of the new gear lube out if you fill and then want to add the FM.

And, you really don't need to wait more then a couple minutes before filling the pumpkin up with lube. RTV will cure just fine even with contact with the gear oil.

 

Permatex the right stuff. That is the name of the product I use. I've used RTV in the past with no issues also.

http://permatex.carshopinc.com/produ...id/42255/25223