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Saying it doesn't need detergents (in this post) is completely different =
to saying 'it needs to be non-detergent' which is what you said earlier, =
and that is what I was questioning. MGA recommendation was apparently =
(https://mgaguru.com/mgtech/gearbox/gt107.htm) for 30wt non-detergent as =
that was commonly available at the time. All the detergent does is =
carry any particles around until they are filtered out by the OD (if =
fitted). It doesn't foam as is often claimed, dish washing liquid foams =
from additives deliberately there to make it do that, who would buy a =
detergent that didn't even if it was as effective as cleaning dishes? =
My Laycock manual doesn't specify what oil should be used, that is left =
up to the manufacturer of the vehicle and how it is intended to be used. =
All it emphasises is that friction reducing additives should not on any =
account be used.
Saying the multigrade properties of engine oil break down over time in a =
gearbox may well be true, but it's a giant leap from there to say that =
means 30 wt straight oil is somehow 'better'.
Do you have a reference for earlier models needing something other than =
engine oil of 20W/50? My period WSM and glovebox handbook state 20W/50, =
although for temperate climates it also includes 10W/40 and 10W/50. =
Temperature ranges below that EXCLUDE 20W/50, and there are no different =
recommendations for 'hot' climates i.e. specifying it HAS to be 20W/50 =
and nothing else.
The V8 gearbox recommendation has always been SAE90 gear oil for =
temperate climates, SAE80 for colder, and I have a BL document somewhere =
that states this for the 4-cylinder as well (although according to the =
link above it shouldn't be used in 3-synch gearboxes as they have brass =
components), although others say that was rescinded. That's not a =
recommendation to put it in an auto box of course, any more than not =
using it in auto boxes is a statement of fact that you can't use it in =
overdrives, which is another giant leap to nowhere. Whilst the gearing =
arrangements use the same principle, the control is completely =
different.
My understanding is that it is only very early non-OD gearboxes that =
were splash fed, and only 1st gear at that, the others fed by a helical =
screw pump, and all four gears are pump-fed on the 4-synch - lots of =
info here https://mgaguru.com/mgtech/gearbox/gt201.htm. That's =
regardless of whether overdrive is fitted or not, although they share =
the same oil the lubrication of each is completely separate. Originally =
that source recommended not towing long distances with the rear wheels =
on the ground, but he says since then he has towed his 150 miles with no =
problems - but the oil level does need to be correct.
----- Original Message -----=20
...
The factory manuals specify =E2=80=9Cengine oil=E2=80=9D for both =
overdrive and non-overdrive transmissions.
If you analyze that recommendation, you would conclude that the key =
characteristic they are concerned about is viscosity. Analysis follows:
Transmission oil does not have to deal with combustion blow-by or high =
heat, so it doesn=E2=80=99t need detergents or protection from thermal =
breakdown. And my personal take on it (though this is apparently highly =
controversial) is that for transmission oil it is better to use a =
single-grade oil, as multi-grade oils break down into the single-grade =
stock over time, and one does not change the transmission oil very often =
compared to engine oil (or ever, IME). It=E2=80=99s not that multi-grade =
would hurt; it is that its benefits, if any, won=E2=80=99t last, and the =
single-grade base stock is equivalent to the lightest grade in the =
rating; i.e. 20W50 breaks down into 20W.
But some people will fly off the handle at the suggestion that 20W50 =
is not ideal. Their logic goes something like this: =E2=80=9Cthe manual =
says =E2=80=98engine oil=E2=80=99 for the transmission; for my climate =
it recommends 20W50 engine oil for the engine, therefore 20W50 is the =
only correct oil for the transmission.=E2=80=9D I believe it is only the =
later model MGs that have this particular recommendation (20W50) in the =
drivers handbook.
Anyway, backing up a paragraph or two, to my mind there is a =
significant difference between the standard transmission, which uses oil =
for splash lubrication only, and the OD transmission, which uses oil as =
hydraulic fluid with a planetary gearset, much like an automatic =
transmission. Automatic transmissions are extremely sensitive to =
viscosity =E2=80=94 I don't think you would have much luck with 90W gear =
oil in an auto trans.
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<STYLE></STYLE>
</HEAD>
<BODY=20
style=3D"WORD-WRAP: break-word; -webkit-nbsp-mode: space; =
-webkit-line-break: after-white-space"=20
bgColor=3D#ffffff>
<DIV><FONT size=3D2>Saying it doesn't need detergents (in this post) is =
completely=20
different to saying 'it needs to be non-detergent' which is what you =
said=20
earlier, and that is what I was questioning. MGA recommendation =
was=20
apparently (<A=20
href=3D"https://mgaguru.com/mgtech/gearbox/gt107.htm";>https://mgaguru.com=
/mgtech/gearbox/gt107.htm</A>) for=20
30wt non-detergent as that was commonly available at the time. All =
the=20
detergent does is carry any particles around until they are filtered out =
by the=20
OD (if fitted). It doesn't foam as is often claimed, dish washing =
liquid=20
foams from additives deliberately there to make it do that, who would =
buy a=20
detergent that didn't even if it was as effective as cleaning =
dishes? My=20
Laycock manual doesn't specify what oil should be used, that is left up =
to the=20
manufacturer of the vehicle and how it is intended to be used. All =
it=20
emphasises is that friction reducing additives should not on any=20
account be used.</FONT></DIV>
<DIV><FONT size=3D2></FONT> </DIV>
<DIV><FONT size=3D2>Saying the multigrade properties of engine oil break =
down over=20
time in a gearbox may well be true, but it's a giant leap from there to =
say that=20
means 30 wt straight oil is somehow 'better'.</FONT></DIV>
<DIV><FONT size=3D2></FONT> </DIV>
<DIV><FONT size=3D2>Do you have a reference for earlier models needing =
something=20
other than engine oil of 20W/50? My period WSM and glovebox =
handbook state=20
20W/50, although for temperate climates it also includes 10W/40 and=20
10W/50. Temperature ranges below that EXCLUDE 20W/50, and there =
are no=20
different recommendations for 'hot' climates i.e. specifying it HAS to =
be 20W/50=20
and nothing else.</FONT></DIV>
<DIV><FONT size=3D2></FONT> </DIV>
<DIV><FONT size=3D2>The V8 gearbox recommendation has always been SAE90 =
gear oil=20
for temperate climates, SAE80 for colder, and I have a BL document =
somewhere=20
that states this for the 4-cylinder as well (although according to the =
link=20
above it shouldn't be used in 3-synch gearboxes as they have brass =
components),=20
although others say that was rescinded. That's not a =
recommendation to put=20
it in an auto box of course, any more than not using it in auto=20
boxes is a statement of fact that you can't use it in overdrives, =
which is=20
another giant leap to nowhere. Whilst the gearing arrangements use =
the=20
same principle, the control is completely different.</FONT></DIV>
<DIV><FONT size=3D2></FONT> </DIV>
<DIV><FONT size=3D2>My understanding is that it is only very early =
non-OD=20
gearboxes that were splash fed, and only 1st gear at that, the others =
fed by a=20
helical screw pump, and all four gears are pump-fed on the =
4-synch - lots=20
of info here <A=20
href=3D"https://mgaguru.com/mgtech/gearbox/gt201.htm";>https://mgaguru.com=
/mgtech/gearbox/gt201.htm</A>. =20
That's regardless of whether overdrive is fitted or not, although they =
share the=20
same oil the lubrication of each is completely separate. =
Originally that=20
source recommended not towing long distances with the rear wheels on the =
ground,=20
but he says since then he has towed his 150 miles with no problems - but =
the oil=20
level does need to be correct.</FONT></DIV>
<BLOCKQUOTE=20
style=3D"BORDER-LEFT: #000000 2px solid; PADDING-LEFT: 5px; =
PADDING-RIGHT: 0px; MARGIN-LEFT: 5px; MARGIN-RIGHT: 0px">
<DIV style=3D"FONT: 10pt arial">----- Original Message ----- </DIV>
<DIV=20
style=3D"FONT: 10pt arial; BACKGROUND: #e4e4e4; font-color: =
black"><B>...</B></DIV>
<DIV><BR></DIV>
<DIV>The factory manuals specify =E2=80=9Cengine oil=E2=80=9D for both =
overdrive and=20
non-overdrive transmissions.</DIV>
<DIV><BR></DIV>
<DIV>If you analyze that recommendation, you would conclude that the =
key=20
characteristic they are concerned about is viscosity. Analysis =
follows:</DIV>
<DIV><BR></DIV>
<DIV>Transmission oil does not have to deal with combustion blow-by or =
high=20
heat, so it doesn=E2=80=99t need detergents or protection from thermal =
breakdown. And=20
my personal take on it (though this is apparently highly =
controversial) is=20
that for transmission oil it is better to use a single-grade oil, as=20
multi-grade oils break down into the single-grade stock over time, and =
one=20
does not change the transmission oil very often compared to engine oil =
(or=20
ever, IME). It=E2=80=99s not that multi-grade would hurt; it is that =
its benefits, if=20
any, won=E2=80=99t last, and the single-grade base stock is equivalent =
to the lightest=20
grade in the rating; i.e. 20W50 breaks down into 20W.</DIV>
<DIV><BR></DIV>
<DIV>But some people will fly off the handle at the suggestion that =
20W50 is=20
not ideal. Their logic goes something like this: =E2=80=9Cthe manual =
says =E2=80=98engine oil=E2=80=99=20
for the transmission; for my climate it recommends 20W50 engine oil =
for the=20
engine, therefore 20W50 is the only correct oil for the =
transmission.=E2=80=9D I=20
believe it is only the later model MGs that have this particular=20
recommendation (20W50) in the drivers handbook.</DIV>
<DIV><BR></DIV>
<DIV>Anyway, backing up a paragraph or two, to my mind there is a =
significant=20
difference between the standard transmission, which uses oil for =
splash=20
lubrication only, and the OD transmission, which uses oil as hydraulic =
fluid=20
with a planetary gearset, much like an automatic transmission. =
Automatic=20
transmissions are extremely sensitive to viscosity =E2=80=94 I don't =
think you would=20
have much luck with 90W gear oil in an auto=20
trans.</DIV></BLOCKQUOTE></BODY></HTML>
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