At 05:02 AM 5/9/2010, Kurt Grotz wrote...
>I have been getting mixed messages about the proper oil to use.  Some
>say
>only GL-4 some say they use GL-5 just fine.  Problem is - I can't find
>straight up GL-4 in any auto supply store.   Thoughts and or
>ideas?    And
>is it SOP to resurface flywheel and replace seal when tranny is
>removed.

GL-5 is fine, as long as it also carries the MT-1 rating.

The reason some say to avoid GL-5 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 generally
eat yellow (copper based) metals, such as used in synchro rings. The
GL-5 spec does not require a test for stability in the presence of
copper and copper alloys. So, without knowing anything else, using a
GL-5 might be dangerous to your synchros.

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

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.

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.
This provides the assurance needed that your synchros are safe.
Synthetics often carry these ratings, since they usually avoid the use
of sulphurous HP lubricants.