At 01:04 AM 3/12/2007, Geza Polony wrote...
>when cold. He tells me to change the Redline to dino GL-4. Problem is,
>GL-4
>is hard to get. The Royal Purple site says their GL-5 won't damage
>synchro
>rings, and there are plenty who swear by Redline. I know this has been
>a
>subject of discussion in the past and have searched the archives, even
>finding another reference to Ron in 2003 who was then giving thumbs up
>to
>GL-5.

If you use a GL-5, it should also carry the MT-1 rating. The reason for
this is that the easiest way to meet the high pressure lubrication
requirements of GL-5 is to use a sulphur based compound (like
molybdenum disulfide). Sulphur compounds eat yellow metals, like used
in synchro rings. The GL-5 spec does not require a test for stability
in the presence of copper and copper alloys.

GL-4 is good because it requires a ASTM D-130 copper strip corrosion
test.

MT-1 (and MIL-PRF-2105E & SAE J2360) also require a D-130 test. If
you're going to use a GL-5, it should also carry one of these ratings.
Synthetics often carry these ratings, since they usually avoid the use
of sulphurous HP lubricants.

ASTM D-130 is designed to assess the relative degree of corrosivity of
the sulphur compounds contained in a petroleum product. The test is
carried out by immersing a polished copper strip in a given quantity of
sample, heating at a temperature and for a time characteristic of the
material and comparing the copper strip after it has been washed and
dried with the ASTM Copper Strip Corrosion Standards.