Well, lessee, in an overdrive friction clutch, isn't the oil under
shear forces? And the oil is at high pressure in the overdrive when
it's engaged. Isn't that good?
I've been using 20W-50 in MGB overdrives for 10 years or so. No
failures yet. Isn't that good?
What I don't understand is why you don't believe that the guys who
designed and built the gearboxes/overdrives didn't know what oil was
best to use in them.
CR
ATWEDITOR@aol.com wrote:
> In a message dated 11/7/2003 12:38:02 PM Eastern Standard Time,
>mvheim@studiolimage.com writes:
>
>
>>I recently unearthed some information to support the
>>contention that one should use single-weight oil in the gearbox (30w rather
>>than 20w50). 20w50 is apparenty essentially 20w oil stock with viscosity
>>improving additives. These additives have their greatest effect under high
>>pressure and sheer conditions (as in main bearings) and don't really have
>>any effect under splash oiling (as in a gearbox). Moreover, these additives
>>break down relatively quickly. In an engine, with frequent changes, this is
>>insignificant; but in a gearbox, one would basically be running 20w oil
>>after, say, 10K miles. How often do most people change the
>>gearbox oil?
>>Think about it.
>
>
> Matt,
>
> Thanks for backing my contention that multi-grade is not the best for the
>tranny, especially with overdrive.
>
> Jay Donoghue
> 73B-GT
> 66 Mustang
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