Ok, So I decide to swap my stock 3.08 gears out for a set of 3.73's. I pulled off the old ring and pinion gears. Pulled the pinion bearing off, moved the shim onto the new pinion and reinstalled with the old carrier shims. I then "painted" the ring gears and checked where they where making contact. The backlash was over specs so I replaced carrier shims. Right now I have the backlash set correctly @ .009 of backlash. My problem seems to be as follows. When checking teeth wear on the drive side with a load the teeth on the ring gear touches on the top toe side "inside" of the ring gear. On Coast it marks on the top heel "outer" part of the ring gear. Now, all the books say to lower pinion shim. So I miked the original it was .027. I went to a .020 shim---small improvement. went to .015 down to .010 to shimless. I still am riding way to far out of spec to call it close enough. I've talked to a few local shops. Most say they do swaps, as I ask them questions they usually stop me and tell me they just use the old ones and don't have a problem. I realize that if your getting paid book time this would probably be how I would do it as well. However, I would like it done right and as far out as it's sitting I'm sure a tooth would break eventually. I have cheked the pinion bearing, the race it sets on and all other mating surfaces. Everything is ok inside the housing. I.E. not loose. I am totally lost?? The gear is made by Ford Racing Products. Could the machine cuts on the gear be the problem?