Last summer I found a replacement diaphragm from Chevrolet. The part no escapes me but mine too was dry rotted. That sealed up the unit on the axle and I have traced the leak to the rotary valve. I removed it and cleaned it and found some sealing surfaces inside but couldn't come up with a material to fix it with.I used to drive an old IH that had a two way valve for the power divider and I wonder if one of these will work.
JHolland
Middle Ga