Answers to various posts...
>From: Ray James <rwj4123@sigma.tamu.edu>
>I used a gear oil (don't remember what viscosity right now) in my
>Midget transmission since last rebuild. I didn't even check the
>specs, so if it (79 1500 cc model) calls for motor (engine?) oil I am
>surprised.
The Spit-engined Midgets (yech... :-) use a Spit trans, not a
Sprite trans. The Spit trans may well be stated as using gear oil.
> The primary difference in the two, in my understanding is
>that engine oil has additives to make the viscosity more nearly
>uniform over a wider temperature range ie, 10W40 will behave like 10W
>at low temperatures
Many/most gear oils are multi-viscosity too (like 70W90). Note
that the numbers used for gear oils and for engine oils cannot be directly
compared... I think a 70W90 is similar in viscosity to a 10W30 or so, but
that's a guess.
>The real attribute needed in gearcase oil, though, is a "high pressure"
>rating. The designations sometimes include a HP or some other
>notation to indicate that the oil is formulated (with additives?) to
>maintain a film under the very high pressures generated when one gear
>tooth rolls over another (almost zero contact area, with a high
HP stands for Hypoid. Hypoid oils (for use with hypoid-mesh gears,
such as in a differential) use a sulfer compound. I vaguely remember
hearing that this might attack some of the components in some transmissions.
(synchros?)
>Summary--I always use detergent oil, multiviscosity, in crankcase;
>gearcase oil in gearcases. If there were a gearcase which shares
>lubricant with the crankcase, it would make sense to use same oil--you
>don't have any choice, right? In that case, I would look for good
>quality crankcase oil, and investigate to see if any make claims as HP
>type oils.
I've never seen a hypoid engine oil. I think the sulphates attack
some bearings or cause other problems.
Sprites (and some others) use transmission components designed for
use in Mini's which run them in the crankcase. So it makes sense that you
use engine oil - it was designed for it.
Interestingly, my '85 Honda CRX also specifies engine oil for its
transmission.
I'd guess it's just a design parameter. A transmission can be designed
either way, at least for smallish 4cyl cars.
>Trivia Quiz--What does the "W" in 10W40 stand for?
Winter.
> Good post by Paul Swengler on DOT5. That is another advantage I
> failed to mention, is it is not a paint stripper. Also MUCH higher
> temperature tolerance. As for it being harder to bleed, which was
> mentioned in a previous post, I've never found that to be the case
I think the issue is that silicone fluid tends to trap tiny air
bubbles, which can cause a mushy pedal. If you're very careful while pouring
the fluid it may help avoid the problem.
I also understand that fresh DOT 4 (or racing equivalents) has a higher
boiling point than DOT 5. The boiling point for DOT 5 doesn't drop with
time & exposure to humidity. I've never heard of racers using DOT 5, though
I'm sure a few have.
DOT 5 is particularily good for cars that spend a lot of time sitting,
such as in a museum or a collection. For a semi-daily driver it's less of
an issue, since the extra maintenance isn't a big deal. Also for show cars
it avoids the chance of a drip bubbling paint, and makes certain your 100-
point cars stays that way. (They need to save the time to toothbrush the
tires, anyways... ;-)
>From: Fredrick Mcconnell <mcconfr@mail.auburn.edu>
>Subject: SCCA autocross/roadracing regions
>
>After renewing my SCCA membership, I have decided that I would like to
>think about possibly autocrossing my '71 MG BGT in the '95 season.
You should also ask on the autox list (autox@autox.team.net).
>Regarding motor oil in gearboxes. Those of us with Minis never seem to worry
>about this. The transmission for the Mini is nearly identical to the Midget
>/ Sprite box, and the Mini does fine with multigrade detergent oil.
Actually, a sprite uses Mini gears I think. (Sprites were introduced
in '58).
Randell Jesup - '70 TR6
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