I'm putting in a clutch/flywheel today and am having a hard time finding the correct tranny oil. I would prefer Diaqueen or Redline MT-90 but no one carries it locally. I would like to get this together today and the only local trans oils I could find where mostly GL5 spec.I'm hesitant to use GL5 as there are so many differing opinions as to the corrosive ingredients in GL5 that may cause the soft metals in our older transmissions to corrode. I did find Royal Purple Max Gear 75w-90 which says it meets both the GL4 and GL5 specs.Quote "The noncorrosive nature of Max-Gear provides excellent results in applications for both GL-4 and GL-5 fluids" After searching numerous forums regarding this topic there doesn't seem to be a definitive answer out there. I've put a call into Royal Purple and they are going to get back to me but does anyone have experience with this particular oil in our cars?