I drained out about 2½ quarts. I put in 4 quarts of oil and it still is not full but close. Should I fill it all the way till it leaks out the fill hole?

Try this link.

http://www.dieselplace.com/forum/showthread.php?t=10816&highlight=rear+diff+fluid

I just changed my rear diff a few days ago and filled it to the level as was posted about 2 month's ago on another thread. There was a new TSB that said not to fill to the 0-10mm level but to fill it to .60"-.80" below the filler plug. I actually made a printed copy off the thread and referred to it. If you can't find it on a search, let ne know and I'll dig it up.

Thanks!

I always fill it to the bottom of the fill hole, how the heck can you accurately measure .60-.80" inside the diff, besides a little too much is better than not enough. IMO

Mine took 3.75 quarts.

I always fill it to the bottom of the fill hole, how the heck can you accurately measure .60-.80" inside the diff, besides a little too much is better than not enough. IMO

Not really. Too much oil means higher internal pressures and blown seals. The TSB also stated capacity was 3.17 quarts.

Page 2 of THIS THREAD (http://www.dieselplace.com/forum/showthread.php?t=10816&page=2&pp=10&highlight=rear+diff+fluid) shows the descrepency that I was talking about. But, read thru the whole thread.

What I use to measure the fluid level is a bent over piece of coat hanger that I use as a dipstick thru the filler hole

Four quarts works fine for the majority. No problem with seals because the differential is vented. Later! Frank

My dealer just changed mine and used 3 qt's. 2004 2500HD. I didn't question him as it's his baby if it's wrong.