Thats it! Thanks T4! It seems like everyone always states that it's bad, but no one really gave a reason why. I researched it as much as I could and was only able to find little tid bits here and there. Castrol's website seemed to be the only site that shows a GL-4 Gear oil.
The dealer actually uses the Hypo-
C GL-5 which I believe was 80W90 grade. He pulled out a bottle and let me read the back of it. I went to Castrols site and saw the Castrol Hypo GL-4 80W90 which looks like the route I may go if I can find it. Here is the one I am trying to find:
http://www.castrolusa.com/products/p...&product_id=15
I read SE-R.net and searched the SE-R Digest and both pretty much states use MT-90 cause it's the best. Not really explaining why or what other alternative gear oils there are.
I am going to look at the link you provided for more detail as well as Castrol's site again. Thanks!