NEW OWNER WANTS MORE ADVICE

Bob K · Post by **Bob K** » Wed Jul 20, 2005 9:33 pm

I would like to know details of the diff. oil for our 1989 1600.
We recently had a thorough service carried out by our mechanic but he didn't
change the diff oil because he couldn't identify the correct grade/type of
oil. The local Mazda agents were no help.
The Mazda database shows that this vehicle was fitted with a limited slip diff
from new. Whether this is still the case could not be confirmed visually,
there being no part number visible and we do not know whether a LSD looks any
different to a standard one. Also he thinks that one rear wheel was too easily
turned with the other held stationary for it to be a LSD.
Anyhow, and the point of my question, can anyone tell me how to confirm the
type of diff and also the correct oil.

Bob and Cath Kingston

Ian · Post by **Ian** » Wed Jul 20, 2005 10:04 pm

Not an expert on this model...but if you drain the oil (save it if you want
to), and you should be able to tell if it has a LSD with a good torch...
Another method is , with both wheels off the ground, turn one by hand and
observe the other - if they both turn 'in the same direction' - you have an
LSD.
If fitted with an LSD ex factory, your car would have a viscous LSD with a 40%
lock up rating (this is very modest). In theory this should not require
adjustment through its life, and was replaced with a stronger Torsen type LSD
in late1993 (manual cars only), and then a Torsen Mk 2 in 1997. Later LSDs can
be retrofitted in earlier cars with other mods (half shafts etc depending on
model). A factory 'clutch type ' competition LSD is also available for your
car.

Cheers, Ian

EricW · Post by **EricW** » Wed Jul 20, 2005 10:15 pm

I have a memory from so far back, (about 1972), that I am not really sure if
it is accurate, but in answering Bob's question someone might be able to
refresh my memory.

I seem to recall from working on the LSD on my Aston that, if you jack both
rear wheels off the ground on a standard diff, when you turn one wheel, with
the other wheel turning free, the other wheel will turn in the opposite
direction, whereas on an LSD it turns in the same direction. Now, that could
be total BS, but as soon as I read the question, that memory popped up.If it's
correct then it would easily solve Bob's problem.

Can anyone confirm or deny this?

Eric

EricW · Post by **EricW** » Wed Jul 20, 2005 10:18 pm

Thank you Ian, I have staved off Alzheimers for yet another day!

Eric

Ian · Post by **Ian** » Wed Jul 20, 2005 10:19 pm

PS My understanding is that factory MX5 LSDs do NOT require LSD oil...
(Personally, I would run LSD oil if I had a factory LSD, and most definitely
would with the competition LSD)
Years ago when racing in a class which only allowed 'open'diffs ie no LSDs, we
ran LSD oil as a form of 'insurance' plus we overfilled the diffs slightly to
counter centrifical forces...

Ian

Ian · Post by **Ian** » Wed Jul 20, 2005 10:21 pm

Eric...you're onto it my man! See my reply..

Ian

animalmagic · Post by **animalmagic** » Wed Jul 20, 2005 10:22 pm

Another method is , with both wheels off the ground,
turn one by hand and observe the other - if they both
turn 'in the same direction' - you have an LSD.

This won't work with a Torsen - it acts just like an open diff under
these circumstances. As Ian says, unless it was retrofitted, you
will not have a Torsen anyway

I would suggest that, unless you
are an extremely gentle driver, you would have noticed the effect of
an LSD when driving, especially the clutch type.

My Torsen takes the same oil as the open diff, though that may not
be true of a viscous diff.

--
Regards Terry

I almost had a psychic girlfriend, but she left me before we met.

--

Ian · Post by **Ian** » Wed Jul 20, 2005 10:25 pm

Thanks Terry...I will be looking for a Torsen for my late 93 1800 in due
course, so will bear that in mind.
Cheers

Ian

Euen · Post by **Euen** » Wed Jul 20, 2005 10:51 pm

Also with Alzheimers lurking around the corner, I seem to recall a stream on
the forum a few months ago regarding oil for diffs and LSDs in particular.

Managed to find a couple of comments from a stream called "Diff Shudders"
(it was actually last July)

"What exactly is the "Mazda Spec Limited Slip Diff Oil" Brand, name etc???"

"the oil came from a mazda dealer,(its mazda branded oil) its made for lsd's
, its expensive but very viscous and it does the trick
a 2 liter pack but you only need 1 liter
h"

"Shuddering LSD's that get fixed with either LSD specific oil, or LSD
specific additive in normal gear oil, are only for clutch-type LSD's.

Early MX-5's had Viscous LSD's and later ones have TORSEN LSD's from the
factory. Neither of these types require, or respond to, LSD specific gear
oil... normal gear oil is fine. Neither factory LSD works on friction, and
thus, friction modifiers will have little if any effect...

The only MX-5's that will behave differently with LSD oil are ones that have
had a clutch type diff installed... the most common being a Mazdaspeed
item, or one from an RX-7...

Fletch."

I think the first thing to do is identify your diff. Unfortunately neither
the Haynes or the Enthusiast Shop Manual are much help.

Cheers
Euen

poison · Post by **poison** » Wed Jul 20, 2005 10:53 pm

Hi All,
What's a Torsen? I know about LSD (that's Limited Slip Diff, and not illegal
LSD variety, before anyone comments

but have not heard about Torsen
before.

Cheers

Gazza
"PO1SON"

Rex Johnston · Post by **Rex Johnston** » Thu Jul 21, 2005 7:19 am

Gazza wrote:

Hi All,
What's a Torsen? I know about LSD (that's Limited Slip Diff, and not illegal
LSD variety, before anyone comments but have not heard about Torsen
before.

<paste from http://www.humvee.net/hid/rungear/diffs.html>

The Torsen name comes from TORque SENsing. The Torsen is not the only
torque sensing diff around.

The Torsen design is based on worm gears, rotating on different axes. It
is extremely difficult to describe w/o a picture. Each side gear is a
worm gear splined to the halfshafts. There are 3 sets of planetary worm
gears (called element gears), perpendicular to the side gear axis. Each
set consists of two worm gears, connected via spur gears, and mated with
each side gear. Thus, the two side gears are interconnected via the
element worm gears.

Note that Torsens are *_not_* limited slip differentials. They are
torque sensors. They are totally different beasts. LS units try to limit
slip between halfshafts in an effort to improve power to the ground.
Torsens bias torque between halfshafts to improve power to the ground.
In almost all situations, torque sensors put the most power to the
ground compared to any other design.

Rex

Ian · Post by **Ian** » Thu Jul 21, 2005 7:25 am

Hi Gazza...

I stand to be corrected, but a Torsen is a newer more sophisticated type of
LSD introduced by Mazda as standard with the Batman RX7 (1992 ish) and
subsequently on the late 93 onwards MX5 (man not auto from what I can
figure). There was probably a Mr Torsen in there somewhere - inventer? The
mk 2 Torsen was a simpler device and cheaper to produce, but no less
effective. Most LSDs have an inherent 'understeering effect' on handling,
but the Torsen addressed this to a degree, I believe...

Cheers, Ian

Grant · Post by **Grant** » Thu Jul 21, 2005 7:50 am

Apparently Torsen comes from TORque SENsing.

Grant.

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The torsen is favoured by some as it doesn't wear out, and has a nice
smooth engagement. (But requires both wheels to have some traction,
ie not be lifted off the road!)

...So if you're a bit of a drifter you'd probably want a clutch-type
LSD instead, which is more abrupt in engagement

On 7/21/05, The Simpsons <grant@simtronics.co.nz> wrote:
[...]

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There is a ton on onfo on toesen on www.miata.net.

Go to the forums and do a search - you will get more info (with pics)
that you could ever use (and generally of a very high quality)

C

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