I believe the Motul 300v and Liqui-Moly are both GL-5 especially the LM because they do not sell a 75w-90 GL-4 in the US market.
Why not try a 75w GL-4? NOT a synchromesh variety...but a REAL 75w GL-4 only gear oil?
I'm personally one of those guys who believes heavier oils protect better, I forget the exact term people label us on here, but yeah I'm one of THOSE guys
Anyways, OEM specs 75w90, and I don't see my self going lower unless it will actually be beneficial other than just gaining a fraction of a MPG. I doubled checked, both LM and Motul do make GL-4 variants. Correction: the motul was a gear 300, not a 300V. One of the reasons I actually tried the LM was because it's not a full synthetic. As GL5 is too slippery for transmissions I thought maybe the synthetic GL4 oils I was trying were maybe too slippery causing the undesirable shifting characteristics. The LM product I got is supposed to be a semi-synthetic(however way they're defining it) and it was a let down too. Atleast at $10 a quart I dont feel terrible with my experiment.