Any froggers with expertise in rebuilding worm drives - there is a thrust washer behind each sun gear in the diff. The part number is 3115.06 and it is a Celoron washer 35x52x1.5mm (Celoron is a type of reinforced bakelite). These don't seem to be available anywhere so I'm wondering if another material can substitute - nylon or brass perhaps? I found a Citroen specialist in France (Jose Franssen) who has several sizes of Celoron washers, bur not the right one.