> A TR3 Gearbox needs SAE 30 oil.
> A TR4 gearbox needs SAE 90 oil.
Triumph's recommendation actually changed before the end of TR3 production,
around 1960. If you check "Practical Hints for the Maintenance of the
Triumph TR3" P/N 501528 (which was effectively the TR3 owner's manual) sixth
edition, it specifies SAE 90 GL4 (gear oil) as well.
Supposedly, the reason for the change was that the factory was seeing too
many failures under warranty, and felt that the "extreme pressure" gear oil
would protect the gearbox thrust washers better than motor oil.
As Dave says, there has been a lot of concern that GL5 gear oil (which is
considered a supercession of the GL4 standard) may contain more of an
additive that can, over time, break down to produce sulfuric acid. The
acid, although not very strong, can attack and degrade the thrust washers
and synchro rings (so-called "yellow metal" because they are alloys of
copper). However, many GL4 oils also contain that additive, just not as
much of it. So my personal suggestion is to look for an oil that also meets
the MT1 specification.
MT1 (Manual Transmission-1) itself doesn't have much to do with our
gearboxes (it's for heavy duty, non-synchronized gearboxes like those found
on large trucks). But it has a requirement for long-term, high temperature
stability that effectively bars the use of the additive that breaks down and
attacks yellow metal.
-- Randall
> -----Original Message-----
> From: triumphs-bounces at autox.team.net
> [mailto:triumphs-bounces at autox.team.net] On Behalf Of email ?
> <emw327 at gmail.com>
> Sent: Friday, April 01, 2011 3:30 AM
> To: Triumphs at autox.team.net; 6pack at autox.team.net
> Subject: [TR] TR3 Gearbox Oil
>
> Hello
>
> I bought a 1959 TR3a.
> I'm nut shure about the gearbox in it.
>
> Does anybody knows from what number of gearbox SAE 90 is needed.
> I all ready drained it, so I don't know if its a synchronised
> first or not.
>
> Greetings from Belgium
>
> Guido
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