Rear Differential gasket and fluid
I have a 2014 GT with track pack 3.73. I recently installed the Ford Performance Differential Cover. After going back and forth with the parts guy at Ford dealer he insisted that this rear end uses 75W-85 hypoid gear oil. He showed me a printout showing that a 2014 Mustang GT takes this fluid. So I swapped my diff cover and put 4 oz. friction modifier and filled the rest up with motorcraft 75W-85. Filled till the fill hole and let it drip out a bit till it was below the fill hole and cleaned it up and drove it. No issues a first, maybe 2 or 300 miles, and 4 quarter miles passes in I noticed fluid all over the rear end. I stuck my finger in and the oil was still at a good level, and looking further it seemed to be maybe leaking from the vent screw on top of axle maybe from being a little over filled. i cleaned everything up again and drove it maybe 50 miles at most. The whole rear end is wet again. So i just purchased some silicone to reseal the differential and went to a different Ford dealer now and they insist the 75W-85 oil is only for the Shelby and I should be using 75W-140. So after this super long story my questions are, Has anyone had any issues with the gasket leaking from a ford racing diff cover? Has anyone had issues with the vent screw leaking? And what weight diff oil is every one running in GT track pack rear ends?
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