Rear-end ?'s need help

I recently rebuilt the rear end and changed the cover with the one from american Muscle.com GMS 8.8 Rear End Differential Cover (79-10) at AmericanMuscle.com - Free Shipping! and I wasn't sure about how much oil it needed. So far its up to 5 quarts and its still not coming out of the fill hole which I thought it should have done by now. I thought stock it recommended 2.8 but I'm not sure if this is good or normal, I don't know if something's messed up or I just need to add more oil still. Anyone have any experience with these covers or the Ford racing one? Any suggestions?
 
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8.8 solid axle fill capacity 3.5-3.75-pints

They make bottle size pumps that fit into a quart bottle. Not very $$ and very handy. Put a flexible tube in place of the stiff one. Pump it out.

You need to use the factory fill hole to check the level. It should be within 1/4-9/16-in below the bottom of the factory fill hole. I use an Alen wrench as a field dip stick. Stick the short end in the hole and hold level. Pull out and see the level.

The fill capacity of the Mustang 8.8 with solid axle is 3.5-3.75-pints (if starting from scratch).

If overfilled, the oil will whip and foam and not have enough room for heat expansion. Changing the rear cover does not change the level of the fluid within the diff. Suspect that a lot of oil will run out if the factory fill plug is removed before the excess fluid is pumped out.

If the oil does not come with friction modifier already added, it will need to be added.
 
open the stock fill hole, should start pouring out, once its done put the plug back in and your good to go
The problem with that idea is that it wastes the fluid, creates a mess. Most importantly, the diff is still too full.

So if you still have to pump some out anyway, why not pump it all and save the fluid and the mess?