Escort speed sensor question

I am trying to remove the speed sensor and it does not seem to want to
budge.  I haven't really reefed on it yet out of fear of breaking the unit.

Does anyone know what metal the base is made out of?  I ask to try to find
out if I am wasting my time trying to take it out (i.e. steel sender
&aluminum transaxle fused together through corrosion).

I need to top up the transmission fluid after having lost some due to a
halfshaft replacement.  Saying that, can I inject fluid through the
speedometer cable hole?  I can measure the amount of fluid lost & add an
equivalent amount.

Thanx,

Ray