2 sources of backlash on 915 diff?

[alexandervdr]

I am a bit confused about measuring backlash on the diff of a 915.
There is the one widely described as the backlash between the pinion and the ring gear.
However, there is backlash too internally in the diff itself: when locking one driveshaft, one can turn the other driveshaft slightly before the ring gear starts to move. (at least, that is the case in my 915). So my question: is this 'normal' ? And if so, how much can the backlash be?

[RogueEngineer]

I also noticed this when rebuilding my 915 with some new synchros and a KAAZ LSD.

To combat this I stripped some solid copper wire and shaped it into a single circle. I removed one of the output flanges and slid the copper wire around the small diameter that the lip seal interfaces with (I think i had the seal removed at this point, though).

When you snug down the screw that holds the output flange in, the copper wire is pinched between the flange and spider gear preventing the spider from rotating and causing the issue you're seeing.

This allowed me to get a very repeatable and clean reading on on the ring & pinion backlash. If I remember correctly it was ~0.0055".