I had this same issue, and was able to resolve the issue using a taper 18 mm x 1.5 pipe plug. I bought the plug from Bel-metric it cost $4. Below are before and after pictures. I had to carefully break away the the first half of the threads to get a flat surface. Hopefully this may save the next guy from replacing the transmission.
Transmission Casing Crack - 2013 Crosstrek
in Crosstrek "XV"
Posted
I had this same issue, and was able to resolve the issue using a taper 18 mm x 1.5 pipe plug. I bought the plug from Bel-metric it cost $4. Below are before and after pictures. I had to carefully break away the the first half of the threads to get a flat surface. Hopefully this may save the next guy from replacing the transmission.