move the driveshaft 2 complete turns, not the wheel - also make sure you have the slack taken up to start - also be precise, then multiply x2, you seem to have a 3.50, not likely
the 'chunk' is the differential, not the housing, but markings are not always there and might not match what's been changed in the last 50 years ... the definitive way to tell is pull the cover and count the teeth, should be looked at anyway because it's not uncommon to find them with damaged teeth from a pinion loosening up or bearing going out
Bill
