[Prowbar]

Originally Posted by James

Should be using this:
https://www.summitracing.com/parts/p...YaAn6zEALw_wcB

GL4 has too much sulfur in it and will eat up the brass synchro. GL5 is worst.

I've always been told that GL4 is used for gearboxes with brass synchro's and GL5 is harsh on said parts. I have GL5 in the rear axle. I'll have to change the oil anyway, will look into it.