According to what I read the gl-5 fluids are a NO-NO for syncromesh. There are soft metals in the syncromesh that the aggressive friction modifiers in gl-5 can corrode and damage. Yet the gl-4 syncromesh fluids do not provide the superior shear protection that a gl-5 for our limited slip diff oil provides.

That's why I was so confused when I thought people were using the same in both. It appears that any full synthetic gl-4 fluid is good for the 6 speed manual. And any FULL SYNTHETIC GL-5 for our limited slip diff.

Those two specs as long as full synthetic should properly lube and take care of our cars. In a pinch oil is better than no oil... Just make sure you put the proper fluids in soon.