GL-4 vs. GL-5 Gear Oil

I found this post on a different Norton forum:

From Silkolene

First of all, let me put your mind at rest: modern 'hypoid' gear oils
(API GL4 & 5) do not, repeat NOT, corrode copper-based alloys, and by
'modern' I mean those made by reputable companies since 1970 if not
earlier. It is true that the earliest oils intended for the special
sliding-contact bevel gears invented by the Gleason Gear Co. (USA) in
1925, which they called 'Hypoid', did corrode bronze and brass, so axle
units which incorporated these gears were built bronze-free. So the
original pre-War advice to avoid the use of hypoid-dedicated oils in
other transmissions was sound. Unfortunately, this persists as a
folk-memory (urban myth?!) to this very day! It just refuses to go
away.

I've always used Valvolene 85w/90 in all my Brit bike gearboxes. This is from their website.
"Absolutely, all Valvoline Gear Oils can be used for both GL4 and GL5. The
concern is the type of sulfate used in the gear oil, as you can not use an
active sulfate for GL-4 applications. Valvoline uses an inactive sulfate
that will not harm any yellow metal such as bronze. This allows our products to be used in manual transmissions that have bronze synchronizers."

That would seem to be rather poor information from Silkolene then.
Check when the GL4 spec oils were introduced - and why the later GL4 spec oils were hurriedly introduced...
Not all GL4 oils had the problem though, it was confined to a limited number of oil producers, with poor choice of ingredients - as mentioned.

Water under the bridge now - but that golden look in gearbox oil is very distinctive.
As are the moth-eaten or discolored looking bushes that come out of anything so affected.
So its a much more modern problem than indicated by that ancient 1925ish mention .....

Redline GL4 - "Less slippery low sulfur formula compatible with brass synchronizers"
http://www.amazon.com/Red-Line-50304-Tr ... B000CPCBEQ

What do you need GL5 in a gear box for, its not designed for that any way, plenty of auto gear boxes run for 100000's of km on engine oil

Indeedy, Nortons for many years just used engine oil in the gearbox.
As long as its wet, slippery and resists rust, all is good.

Gear oil has additives that suit gearbox use though, it must be said.
Many modern auto boxes will judder if they just use engine oil.
And very heavily loaded differentials need all the protection they can get.
Its the black magic that does the trick.....

OIL THREAD!!!!! WOOOOHOOOO!!! :mrgreen:

Gearbox oil thread though.
Haven't had one of those for, oooo, 3 weeks or more.....

End of thread.