Just wanted to point out that you should NEVER use brake cleaner (or any chlorinated solvent) prior to welding. Welding causes the brake cleaner to decompose into phosgene gas which is extremely toxic and can kill you.
I know this is an old video. But you never clean a diff with brake cleaner to weld one solid. Brake cleaner will kill you burnt off by welding even trace amounts. watched a guy permanently kill his brain to near vegetable stats few years bake welding a brake cleaner cleaned item.
JB Weld is actually a very good adhesive, with great tensile strength. My ME engineer buddy tested some lap shears, using this epoxy, and it had very similar results to adhesives used in the composites industry, but at a fraction of the cost.
You should have packed it with JB Weld! Like basically fill it to the case with JB weld so the gears are bricked together! I honestly think if it was completely full it might work