Trevor,
Did the Castrol have a "GL rating" anywhere on the bottle? I have always
heard that most GL5 and GL6 gear lubes have higher sulfur contents to
help protect the ring and pinion from shock (not electrical :}). I was
also told, and I read once that this combination of gear lube and sulfur
can be very corrosive to brass, bronze or copper. Which is what most
bushings, and syncronizers are made of.
HOWEVER, some new information I have recieved from two oil companies
claim it is safe to use a GL5 in manual transmissions. It appears that
the corrosive action only takes place when the gear lube gets to hot and
starts breaking down. The one company also said that a GL5 would be
better in a Overdrive transmission that uses planetary gears. Sound
familiar? I have been asking questions specifically regarding the OD
both Triumph and Volvo used. What I am trying to pin down now is at what
temperature gear lubes start breaking down at. I know for a fact that
Synthetic can stand a much higher temperature than conventional oils. As
soon as I can find some good numbers, I will post them.
If you find a GL rating and it is a 4 or lower, your transmission will be
fine but your differential will suffer.
Pat in NC
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