Tightening of an LSD?

[spetz]

Can I tighten a helical type LSD by using thicker rings or something like that?

Factory LSD...

[bennjamin]

there are shims on either end of the worm gear housings ,
perhaps thicker and less shims would increase bite. But no doubt increase wear and reduce life.

[string]

Replace the spring washers in the centre with some high quality new ones - but you will literally have to pull it to pieces to do it.