I have read several threads about torque tube leaks, the cork seals tend to be prone to leaking especially at the threaded collar. I used rubber seals recently and still had a leak but not from the rubber seal so I figured the oil was working back around the threads and leaking out.I cleaned the area around the collar and applied some of the Permatex gasket maker and so far so good. However there is drawback with the rubber seal if you want to remove the ball and collar. Apparently once the seal gets oil on it the seal swells up and becomes EXTREMELY TIGHT on the torque tube making the threaded collar very difficult to move along the torque tube.
The gear oil gasket maker was used on the shafts of my transmission where they go into the case. The shaft that leaked was below the input shaft so gear oil would leak out the front of the transmission and work its way to the bottom of the transmission and drip-drip, some of the oil also went into the splash pan and dripped out of there. This past winter the transmission had been disassembled for new bearings so that was an excellent time to apply the gasket maker as a sealant on that shaft, and that leak is now gone.
