Mike, Clean it good and drive it enough to see where it is coming out. Sometimes the flange has such a bad groove, it wont seal. Also the area where the seal seats in the housing may he pitted and leaking, add some sealer to the outside edge of the seal. Last place is the splines, they need a little sealer put on them before you put the flange on. You can add a little sealer under the pinion nut washer... As stated prior... Make sure you mark the pinion, nut and flange, BEFORE you take apart.. Then just line them up when going together. If you failed to mark them the first time you replaced the seal, your up a creek...You will have gear whine, or eat up pinion bearings... The pinion preload will have to be set correct. The axle will have to come apart... If your flange is grooved bad, try to sand the groove out. You may have to replace the flange.. Good luck..