Rockwell Sq100 - very high backlash

Sounds like a Detroit locker.

Usually the only way to check backlash is with the carrier assembly out of the axle housing. I don't know of any other way to get a dial indicator on the ring gear to check the backlash.

 

If its what I'm thinking, its a screw that threads into the housing and is meant to keep the ring gear from deflecting too far under load. I'm a bit foggy on the name but I think its called a thrust screw, jam nut just locks the screw in place. I don't know the spec on how to set it but I do know that it normally should not make contact with the gear.

 

I don't believe it would. From what I remember the only time the screw actually does anything is when the axle is under high load and is being deflected away from the pinion. Normally I believe it should run with a slight gap between the screw and the ring gear.

 

I haven't worked on one of these in a very long time so my info could be a bit off.

 

The thrust screw shouldn’t touch the ring gear unless it’s heavily loaded.
It’s possible that it will touch if it’s adjusted wrong or the diff case bearings are loose.
Some of those axles had a block of steel on the end of the screw so hopefully it’s not loose enough to let it get off the end of the screw. some just had a screw with a rounded end. Either design you tighten the screw till it hits the ring gear and then back off 1/2 turn. Don’t use to much force to tighten it, just snug with your fingers and a short wrench.
The screw won’t affect backlash unless the case bearings are really loose. If you’re just turning the drive shaft and feeling when it takes up it’s going to have a decent amount of play even with backlash set properly.
There’s no way to actually check the backlash without removing the chunk from the axle housing