On my diff (salisbury) I had to use a 3 ton bottle jack and a 32 socket welded to a 25mm roundbar about a foot long to get that nut to move. Had to jack up the socket against the Landy's weight to get the nut to budge. I found a seal at the engineering supplier , black pvc no metal double lipped with innerspring tensioner measuring 80mm outer & 47mm inner, intended for some or other truck. In $'s it cost $2.00. It fitted well with no leaks to date. Do you really have to buy that weird land rover seal?