Re: Lube level in front diff?
1/2" below the hole is nothing to be concerned with and probably where it needs to be. The diff is a closed system so unless you have a leak there's no reason to top off.
I filled my rear to be level with the hole and it squirted stanky grease out the vent pipe for a few weeks, really nasty mess.
If you don't agree it won't do any harm. Funnel and tube would do the job or just squirt in from a bottle.
2006 E350 6.0PSD 5R110, SMB 4X4, RB-50, ARB lockers front/rear, Aluminess galore, AMP steps.