Brad :
If it works for you, go with it !
Here's what I've been able to piece together :
First of all, the problem is not really related to GL4 vs GL5 specification,
the GL5 standard actually has a tougher limit for copper corrosion.
The real problem is a particular additive, used to increase the 'extreme
pressure' properties of the oil, and which conventional GL5 typically has
more of (because it has to meet a higher standard for EP). This additive is
a sulfur compound, which can break down at high temperatures and form
sulfuric acid. The same additive is used in conventional GL4 oils (at least
some of them), just not as much of it. This additive is mostly what gives
EP gear oil it's distinctive smell.
However, the base oil used for synthetic gear oils naturally has a higher
pressure resistance, and so needs less of the additive. According to
Redline, their MTL (which is a GL4 rated gear oil) has none of the additive.
I've noted that the Valvoline synthetic (which I use in my diff) has very
little of the 'gear oil smell', so I believe it has little, if any, of the
sulfur additive, and so should be safe for use in the gearbox.
However, Ken Gillanders at BFE has reported problems when using Redline MTL
in racing Triumphs, apparently because it is too slick. The specific
problems reported were slipping out of 3rd gear (under downhill hard
braking), and difficulty shifting into 2nd gear towards the end of the race.
(ISTR these were different people, but I'm not sure. Both were on freshly
rebuilt boxes.) The first problem was cured just by switching back to motor
oil, the second one required replacing the 2nd gear synchro (which was done
frequently until they switched oil).
Of course, lots of people use synthetic, including MTL, and have no trouble
at all, so your mileage may definitely vary !
Randall
59 TR3A
Brad Eells wrote :
>
> Hello everyone,
> I have a question about the proper lubricant for non-overdrive gearboxes:
>
> Any thoughts about GL5 vs GL4 vs synthetic? I have always felt
> synthetic was
> the way to go, but now...
///
/// triumphs@autox.team.net mailing list
///
|