Typically would not recommend moulded concrete as shoring. It is not structural and susceptible to shattering under a pinpoint load, such as that it might experience at the hard metal edge of a jack stand. A fresh 2x6 or 2x10 would actually be better in your
application.
It is 100% okay to lift from the differential housing, and even better in many respects to lifting from the axle tube or spring plate.
What bolt did you strip?
I would NOT recommend removing the u-bolts. If you feel you must, consult a factory repair manual (NOT a Haynes or Childress single volume book you get at local parts shop) to see if it requires u-bolt replacement. Many, or perhaps most, will require replacement as these bolts stretch and are not suitable for reuse in a lot of applications. I don't have torque specs handy, but they are usually well north of 100 ft-lbs., often north of 150 ft-lbs. You'll also want to ensure your torque wrench is up to the task as average torque wrenches may not necessarily go that high. I should also point out the the upper 10% of a torque wrench's range (as well as the lower 10%) is typically understood to be non-usable UNLESS the torque wrench's manual explicitly states this.
I agree - most everything is shut down - so this concrete had to suffice.
Thanks - will definitely get something more sustainable soon.
I stripped a lug nut.
I wanted to unbolt the U bolts to get between the leaf plates - to clean and lubricate.
Who knows where the sound is coming from.
Maybe I'll get my son to hop on the carrier and I'll audibly try to figure out whats creaking back there.
But that means I'll have to get the wheels back on before he hops.
Thanks for the tip about torque wrenches. Mine goes up to 200 lbs.
But its a long range torque wrench - i think 40 to 200.
Therefore I know accuracy goes down but generally the central spectrum is more accurate than either extremes.
Thanks for all your input, tplee.