[TR] TR3 Overdrive Transmission Lubrication Requirements

[Randall]

> In all the sources I have, the recommendation for a Trany with
> overdrive, is 30 weight oil. What is the opinion of the list on this
> topic?

That's one of those with no clear consensus.  I've used Valvoline Racing
20W50 for many years, as recommended both by Ken G. at British Frame and
Engine and Herman van den Akker.  Seems to work well; but since I always
have to try something "better", I've recently switched to Redline MT-90.
Too soon to say if it's really any better or not (I'm reasonably confident
it had nothing to do with my gearbox failure).

Standard-Triumph's recommendation did change over the years; and I believe
that, by the vintage of your TR3A, they were recommending 90 weight GL-4
gear oil.  (Practical Hints, 6th Ed)  The story I've heard is that Laycock
(makers of the OD) never recommended "gear oil" as they felt it might
shorten the life of the OD clutch and/or cause "sludging".  (And in fact,
there is an early service bulletin to that effect, apparently as a result of
warranty returns of overdrives.)  However, S-T eventually decided that they
were getting too many returns for worn thrust bearings, and switched to
recommending gear oil.  

However, even GL-4 contains an EP (extreme pressure) additive that can
corrode the brass thrust washers and synchro rings over time, which is why I
prefer the Valvoline Racing or Redline MT-90.  GL-5 contains much more of
this additive (which is why everyone says not to use GL-5), but GL-4 still
has some.

But for no more miles than most people put on their TR3s, I suspect it
doesn't make any real difference.

Randall