I Know this is a subject that has been discussed before but I am Gonna change my rear end lube with 75w140 either royal purple or amsoil
They both say they have the additive in it for limited slip are you suppose to put in the ford additive w it ?

 

No your good to go.

 

Ok I wasn't sure if it was enough in them or if i would have to add some

 

You may just check the concentration to make sure it's enough. The 10.25" takes at least 4 oz I think. Maybe even 8.

 

I used Royal Purple and the smelly stuff from Ford's.

 

I always suggest to use a gasket and Gasgacinch sealer instead of just sealant on the cover. Check the vent up in the frame to make sure it isn't clogged. Drive 100 miles or so and re-check the fluid level.

 

^^ the gasket is the way too go!

 

Ok got the felpro gasket and 4 qt amsoil sever duty 75w140 I am gonna change it sat if we don't get hit to hard w snow

 

While it's apart there's always the 08+ aluminum finned diff cover you could do too. It's pretty reasonable price-wise and seemingly a decent upgrade. Part #8C3Z-4033-A
<table width="330" style="width: 248pt; border-collapse: collapse;" border="0" cellspacing="0" cellpadding="0"> <colgroup><col width="330" style="width: 248pt; mso-width-source: userset; mso-width-alt: 12068;"> <tbody><tr height="20" style="height: 15pt;"> <td width="330" height="20" class="xl63" style="border: 0px rgb(51, 51, 51); width: 248pt; height: 15pt; background-color: transparent;"></td> </tr></tbody></table>

 

Would it have a drain plug

 

Don't think so

 

You'll need longer fasteners for that Ford aluminum cover. 12 total 5/16-18 x 1.25". Or so its said.