One sets up the old fashioned bevel boxes with very little backlash. I had to rebuild mine after I lunched the input shaft and I could find nothing written. So I made sure the thing could go all the way around (four turns of input shaft on an old one) didn't bind and had a teeny tiny bit of extra movement to allow for heat expansion.
Then got it examined by an experienced three wheeler owner who was happy with my efforts so put back and car driven!
In your case though, the 'backlash' you are seeing could come from further forward, but the sound is coming from the box if you get my drift.
