[TR] Red Line Oil

[Randall]

Thanks for the information, Sam. 

I wonder what they consider "low offset" to be?  The TR differential
certainly has the pinion nowhere near the centerline.  And relative to the
gear size, I'd say it was about the same as my RWD Buick wagon (which
specifies GL-5).  From the text of the letter, it seems that they are
assuming our differentials are "low offset" only because they were
originally specified to use GL-4 oil; yet the GL-5 spec did not exist at
that time.  In other words, Triumph specified the highest level of "hypoid"
protection that was available; for gears that (according to legend) only had
to last 7 years.  Those of you with later cars may recall that Triumph also
advised to never change the factory oil (which could be because it was
better than the run-of-the-mill GL-4).

I still find it surprising that an oil designed to have a higher coefficient
of friction is a good choice for gears that need no friction.

Anyway, I'm going to go on using the "extreme pressure" GL5 that has worked
well for me for over 20 years of daily TR driving.  Paying $16/qt or more
for an oil that doesn't work as well as the $8/qt stuff just seems kind of
silly to me.

-- Randall