Drain yer diff oil, if theres heaps of swarf comes out with the oil its a sure indication something aint right. Remove the prop and see if there is movement on the pinion. Might explain why the seal went in the first place. I take it you have done the basic things like check wheel bearings, props UJ's etc??????
If in doubt get some help as it's a fairly big job to remove the front diff... Two heads are better than one and you don't want to go through all that work and find out its something silly!
Bertie.