I use a 23mm Snap-On box end wrench for the fill bolt, never had any issues.

 

This.

I use Amsoil 75w-110

 

I've used the 75w-110 available locally at Salvo Auto-parts but Honestly I find that the Lucas 80w-90 Heavy Duty keeps the diff quieter at cruising speeds. Always seemed to get a slight whine while using the 110 weight but the 90 weight Lucas has been awesome so far!

 

Just use a wrench. It's not rocket science...

 

redline heavy weight shockproof