I recently went on a crusade to get rid of the leaks on my k5. One of them was the leaking rear output on the slip yoke. I know this is a common problem with this set up, because a lot of the people I have talked to have similar problems. I started off doing what most of us have tried, yank the seal and put a new one in, along with all the other little tricks, polish the slip yoke shaft etc. A few days later I noticed it was still leaking, and of course the underside was covered with fresh ATF. I took a close look and noticed the shaft was dry. So I had a feeling that my problem wasn’t the seal. I pulled the drive shaft and disassembled the slip yoke end so I could get a good look at it. I was afraid that it might be cracked and that was causing the leak. I hit it with a hammer in a few spots to listen for any kind of unusual noise. Everything seemed ok. I then filled the inside of the shaft with ATF to see if I could get it to leak. Pretty quickly the ATF started to appear in the center of the yoke. I had found my problem. Judging how the shaft is constructed, it looks like the yoke is machine welded onto the shaft and there is an end cap that goes between the yoke and the shaft to seal it from leaking. And you would have to cut the yoke off the shaft to get to it. I suppose it could also be a cracked end of the shaft its self, but I doesn’t really matter one way or another. The solution: I scuffed up the area around the leak including the cap. I also scribed a grove around where to two pieces look like they meet. I gave it a thorough bath in solvent, and used some JB weld for one of the few things I trust it for. I filled the recess in with the JB weld so there would be less chance of a problem later on. Its been about a week and everything is dry as a bone. I would imagine there are some guys who know about this, and there are a lot of guys like me who have been frustrated trying to get rid of this leak, so I figured I would pass this on.