could be low and your thinking its over filled

my 742 leaks at the pinion seal,when its at the full mark,it will drip oil for a few days and stop..(not driving it anywhere)

then its low,I can start driving it and it will leak some as it oils the front pinion,gets even lower

so I keep an eye on it and as long as its driping the rust prevention I know its full at a glance

also if you check it jacked up in the front of car it will read low on the mark and will be over filled when level

you should be able to R&R the seal on the 742 pinion,it is set up with a spacer and shims

seal will cost a few bones for the 742 case,the leather ones are not that great and leak,use the newer neoprine one

DoctorDiff has them in stock