The car has 40k on a rebuilt engine and trans so I had to try to fix it. It was a 300 dollar car so I had nothing to loose if I couldnt stop the leak. My guess is the PO changed the rear tranny mount and didnt align it right in the 2 positioning grooves on the carrier. Im told thats the most common way to crack it. The way I fixed it was as follows. First step was to drain the tranny for 2 days with the pan off . I had to get ALL the fluid out. Then I used paint thinner and a rag to super clean the area around the crack. Next I used an awl to push material from around the crack into it. The tranny case is soft aluminum so a steel awl can move it around pretty well. I did the awl thing on all parts of the crack I could reach. I cleaned the area again with thinner and then with brake parts cleaner for the residue. Then I used good 'ol JB Weld. I pushed it into the crach as much as possible and then filled the low spot the awl created around the crack. After it dried for a day I sanded it down to fit the contour of the pan gasket trough. When I put it all back together I used B-Sealant on the gasket all the way around. Its been 3 months and still no leak. I was told by my mech that the trans was terminal with a crack like it has so im happy so far. It may start again in time. An awl and JB Weld is no substitute for a solid trans, but for the 300 bucks I paid for the car it was the way to go for me.