I have an owner's manual reproduction for my '63 +4 (from ISIS) and
its says to use 90 weight for the trans and diff. It's interesting
to note that apparently some manuals suggest 30 weight. According to
Notes on Lubrication" I found on the Net and put out by Red Line:
"Gear oil viscosity is measured at 150 F vs. 210 F for motor oil.
Therefore, 40 W motor oil is the same as 95 W gear oil."
If this is correct, 30 wt motor oil has about the same viscosity as
90 wt gear oil. If this is so, then we may only be talking about the
"hypoid" factor. I am now strongly tempting to try 30 wt oil to see
the difference in my tranny, since straight gears are not supposed to
need hypoid oils and more friction may help the synchros (can the
Moss box really be tamed?). By the way, has anyone contacted the
factory and asked?
Armando Picciotto
'63 +4
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