Phil and others,
Gear lube uses a different viscosity scale than engine oil. 75W gear
oil is much thinner than the 75W engine oil preferred by many Harley
riders. 90W gear oil about the same as 40W engine oil.
Gear oil works better on gears than engine oil because it includes
additives that "etch" the gear surface and keeps the lubrication in
place. This same lube attacks brass and this is why most older British
transmissions use engine oil. The lubrication is still OK while the
brass lasts longer.
I have experimented with a variety of lubricants in my MGA trans. My
Moss equipped car is still apart. Slicker (Mobil 1 15W50) or "etching"
(gear lube) oil seems to quiet the box but also reduces synchro
efficacy. Heavier (40wt) oil quiets the box and keeps the synchros
working but slows the shift action. Lighter oil help shift feel and
synchro action but you can hear the gear whine from across the street.
I finally settled on Valvoline 20W50 oil as it seemed to be the best
compromise.
As always, my opinion, no financial interest, YMMV, beware of Greeks
bearing gifts or engineers with time on their hands.
Regards,
Bill Eastman
FYI- I sent this to Phil yesterday but forgot to copy the list.
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