I got the 10 bolt posi rear end out of my car and on jack stands about to rebuild it. I started dissassembling but when I took out the pinion shaft lock bolt I noticed that it was snapped off and the majority of the bolt is still running through the pinion shaft making it impossible to take apart any further... I think. I tried to drill it out but there is not enough clearance to get the drill in straight (because of the housing) and also the bolt is a very strong grade making is difficult to touch with a drill bit. I am willing to break things that can be replaced in order to take it apart. Any suggestions on the easiest way to get this rear end apart???

 

That's very common on GM diffs. There might be half a thread still holding it in. There shouldn't be any torque on the remaining bolt since the clamping force is all done on the head of the bolt. Use a dental pick to try and back it out. I've had very few that wouldn't come out.

 

Being that there is a lack of room to work with, it seemed to be impossible to use an easy-out and I wasn't able to grab it with anything to pull it out. I ended up using a grinder and gring a slot right over the top of the pin to get access to it and push it out (obviously ruining the posi unit... no big deal it was old & abused).