Rear end problem help

Don't know if it helps but I just went thru the same issue of whining on deceleration in my 73 Sport with 8 1/4 and sure grip. The pinion depth was wrong. I added a 0.003 shim under the pinion and reset the backlash from 0.011 to 0.007 and the whining went away. Also, one poster recommended Prussian Blue to check backlash. Please get some marking paste made for the job. I tried Prussian Blue with terrible results - could hardly see the pattern. Picked up some of the baby-**** yellow paste and it worked much better.