[rstolz]

Correction, i had it backwards, GL-4 is what you want, GL-5 can corrode soft metals. GL-5 is mostly for differentials alone (AKA RWD/4WD vehicles where the differential is usually a separate assembly (there are exceptions)).

I almost wrote a scathing reply, then saw your correction...

You need GL-4 oil. Or if you DO get a GL-5, read it carefully to ensure it is GL-5/GL-4 compliant. Those do exist, but you need to be certain.

75W-80 GL-4 is fairly common for FWD Transverse mount transmissions with integrated differentials. VW, Audi, GM, Nissan all use the same spec oil for transverse applications.

Now, notchiness in shifting may also be caused by a shift mechanism out of alignment. I haven't had to mess with mine yet, but I will soon as my 2nd and 5th engagements are nearly at the top of my lever travel.

Try the head of a 17mm bolt in the drain plug.