I hope by now you have the leak repaired. I just put another rear diff on my bike last night. I replaced the original diff last spring due to the ungreased pinion splines syndrome. After 4 months of moderate use the rear tire started spotting with fluid. I replaced the seals and it never made a difference. Tore the diff down last Friday and mic'ed the needle bearing area on the Ring gear spindle. Don't know the mileage of this diff before I got it but I put over 5000 miles on it. The spindle had several thousands of wear where the bearing rides and apparently was allowing the spindle to move at higher speeds enough to let the fluid seep through. Got a diff on flea-bay that is SUPPOSED to have only 4700 miles. Got it sent to me for $206.