I am bringing up this old thread from the dead.
I am changing out my diff oil and was going to go with Redline synthetic. The problem I found was how difficult it is to find in a local shop.
So I opted for Mobil 1, 85W140 rated GL5 for light trucks with limited slip diffs. At $16 a quart, I hope it is good stuff.
I changed out the fluid in the front diff last night and it held nearly 3 quarts before it started coming out the fill hole. I'll do the rear diff tonight. Big Mike listed the capacity at 2 quarts per diff. Am I overfilling by getting gear oil to the fill hole level.