12 bolt problem

[pokerflatoutcast]

Howdy, I had my 12 bolt 373 rebuilt about 6 years ago, and maybe have 5k miles on it. I put a powertracks no slip in it, and a Richmond gear set. Well, I dropped the oil the other day, and saw a lot of fine fine metal in it. no real chunks. Then I see on the drivers side, next to the main bearing cap the shim is dang near all the way out.. I am sure another one was ground up, causing the metal in the oil. I have never seen this. To my surprise, the gears look good, and are tight, though I don't think it was good on it at all. To be honest, I am sick of the 12 bolts. If I cant fix this, it will be the 4th failure I have had with this rear end. I guess I am asking what would cause this? If I didn't have good tires and rally wheels, I would go 14 bolt. well, and also that I have a grand in this pile...