Re: Red Line gear lube question(s)

[Matthew Killick <m.killick@domain.elided>]

Mat asked: 

>My under-bonnet sticker calls for a GL1 oil, but both the MTL and MT90
oils >are GL4.

Wrong.  It actually says 90EP

>I am under the impression that the degree of friction maintained is an
issue >as far as the working of the synchromesh is concerned, and that
there may be >problems of corrosion of some metals in the box, depending on
what additives >are present in the oil used.

>So, does anyone have a justification for the use of a GL4 oil in general
and >Red Line in particular?  I assume that if it is appropriate, then the
MTL >would be the correct choice.

Mat has now done a little homework, and come up with the following:

>From Dave Granquist <Dave@domain.elided>

>My guide calls for a 90W GL-5 in the 1969 Alfas, it shows the GL-1 being
>discontinued in '67. If the GL-5 is called for then the 75W90NS is
>recommended, if it calls for the GL-1, then use the MT-90.

>Thank you for your interest in Red Line Oil.

Carl1750 <Carl750@domain.elided> asked the following:

>For Giulietta and Giulia all the manuals say is 90 in the gear box and 90 EP 
>in the differential.  Today everything is GL 1 or GL 5.  Can somebody 
>translate.

Gear oil is acidic, motor oil is alkaline. Gear oil needs very high wear
protection  Extreme Pressure (marked as EP). Therefore, it has a very high
sulphur and phosphor content. This additive is corrosive to copper bearings
and bronze synchro rings. 

Friction modifiers make the base oil much more slippery. They coat the
metal surfaces, and prevent the stick/slip mode of operation, preventing
shudder, and causes smoother takeup. Friction modifiers may detract from EP
characteristics. 

Gear Lubrication Ratings 

GL1    No Additives
GL5    High sulphur, for heavy duty hypoids

GL5 Should be used in rear differentials. 

Red Line 75/90NS has No Slip, i.e., no friction modifiers.
Red Line 75/90 has Friction Modifiers.

So there it is: MT90 for original pre-67, 75W90NS for re-built and post-67.
 For those of you with original 1967 gearboxes, hahahahahaha.

Cheers
Mat

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