Ammount of Dif. Lash
 

I’m feeling a little slop in my driveline, when backing off or speeding (?) back up. Flex disks and u-joint seems fine. Seems like the lash in the diff, but shouldn’t you have a little play there?

The clearance between the ring & pinion should be 0.004-0.006", that is so small you need a dial-indicator to measure.

Hypoid backlash rarely changes over the life of the axle unless the tooth surfaces wear in which case they will usually get noisy.

The differential gears can wear, and on limited slip diffs, the clutch packs wear. Both of these wear phenomena increase axle yoke end play and differential gear backlash, which usually manifest as occasional clunking noises and increasing driveline lash.

The unit will usually continue to function with significant wear of the various differential parts, so you either live with the wear, or at some point, pull the diff and overhaul it.

Duke