Axle Question about Spreader Tool

Is it really necessary to have one? I just can’t see a cast iron housing moving much. I would think it would crack. Please explain?

Tim, you are only spreading it around .005" max. The spreader allows you to load the carrier and get some preload for the carrier bearings. The diff housing is tougher than you think. I have stripped the threads on the spreader before I got the adequate spread. Not on a Jag but they do take quite a bit of cranking.

Ok, Sounds good. I’ve done pretty much everything, except a differential rebuild.
In the past I’ll just swap units.

Also thinking of swapping to a 3.31 : 1 set if I can find one…