Rear differential

Discontinued.

You can not apply enought torque to ruin the rear end.

Do this a couple of times until fixed:
Tighten the nut on the yoke and drive around and see if leak.

If you can not tighten the nut anymore and you still have a leak. LOOK AT THE YOKE. Is it wore down where the seal goes on to the yoke. Sometimes the spring on the seal will wear down the yoke in one spot.
If so then replace yoke and seal.

On my rear ends, I tighten them as much as possible. Never destroyed a rear end in my life.

I think mech created the whole ruining your rear end so that people would not work on there rear ends.

Remeber the whole replacing a/c system from R-12 to R-134a and replacing lines. Some people spent around $1,000 for nothing.

Still to this day I flush a/c out and put in R-134a oil and ref and they never have a problem.
Last car I did was a 1981 Honda Accord 6 months ago.

I would have to agree with gschretter. They books all say how difficult a rear end is to re-build, critical shimming, pinion depth, backlash, preloads...etc. I re-built my limited slip complete set of bearings, races, ring and pinion gears. My first attempt came out perfect. Didn't even need all those fancy tools they say u need, dial indicators,depth micrometer, race installer's...etc. you should use a yoke holder bar, I made one, welded a 1/4 steel plate on 2 1/2 foot uni-strut, then drill two holes to match yoke u-joint bolt patern (two diagnial from each other) and a big hole for the 1 1/4 socket for the pinion bolt. Mine is torqued to 450 lbs' and use loctite #271.