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Atwell Haynes sent the attached clarification regarding one of my
conclusions in the OD Survey. Since I couldn't have stated it better, I
am forwarding his EMAIL in its entirety.
Regards,
Joe
--
"If you can't excel with talent, triumph with effort."
-- Dave Weinbaum in National Enquirer
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Date: Sat, 20 Feb 1999 20:01:37 -0500
To: Joe Curry <spitlist@gte.net>,
From: Atwell Haines <carbuff@nac.net>
Subject: Re: Overdrive Lube Survey
At 03:17 PM 2/20/99 -0800, Joe Curry wrote:
> J TYPE
...
>4. When the transmission is cold, sluggishness or slippage is observed
in some conditions.
>5. The problem in #4 goes away when the weight of the transmission oil
is reduced.
>CONCLUSIONS:
...
>3 [...] slippage that occurs when the car is first started on
>cold mornings may be solved by going to a lighter weight oil.
Joe, this conclusion is not totally valid for the Spitfire J type o/d.
Using a lubricant with a different friction characteristic from a
(too-slippery) modern hypoid oil is what is needed for the o/d clutch,
which is what slips at start-up.
So by using a straight-weight SAE 50 engine oil, you have the same
viscosity as a 90W gear oil. That's because engine oil is tested/graded at
much higher temps than a gearbox lube. Downside is that the high-shear
characteristics of hypoid oil (ooh that smell!) that allow the gears to
slide are not formulated into engine oils.
I learned this at the Red Line Oil website.
Cheers,
Atwell Haines
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