I emailed Redline and asked about the GL-4, GL-5 gear oils and corrosion, and
their recommendation re: what oil to use with the OD. My original manual
for a TR4A says to use 70-90 EP gear oil. I know that other manuals say
something
else for the SAME OD! Anyway here are their answers:
GL-5 brass corrosion. Only a problem at elevated temperature (300 degrees), but
the redline GL-5 does NOT cause corrosion of brass at anytemp. BUT it will
discolor the brass at high temps. NOTE: Most street transmissions never reach
that high a temp, so any GL-5 ought to be OK.
About the best match for 1967-era 70-90 EP gear oil? They recommend their
MT-90.
-Tony
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