Cribbing is solid wood 4X4 blocks 18" to 24" long built up by laying two N-S followed by two E-W, etc. In this case the top one goes across the pinch weld. I am not a fan of jack stands or ramps and use cribbing to support anything I don't want to be crushed by.
The dowel is held against the part in question and your ear. Any noise will be transmitted along the dowel and be clearly audible.
I suppose I should say that using the engine to turn the rear wheels while they are blocked up is a dumb idea. In this case you would probably need an assistant to turn the rear wheel while you touch the end of the dowel to the hubs and points around the differential.
Greg
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