The Diff in my 85 Type L Automatic is just starting to get noisy. Not unusual as I have owned six mark IIs and they all seem to have diff noise. Some much worse than others. I'm trying to get this one nipped in the bud before it gets too loud and needs a re-build. I read a couple of times that Ford Motor Company LSD 75-90 synthetic lubricant works best in our differentials and keeps em relatively quiet. Has anyone tried it? Also I called to enquire about this product and was told all they have is "75-140". Would this be a problem in an older diff: (140,000 miles)?