LSD question.

alexpav · Postby **alexpav** » Mon Aug 06, 2012 1:47 am

May be a silly question but....
Every LSD- when spinning one side...the other HAS to spin the same way?
If it spins the opposite, there is no way this is an LSD? any exceptions?
When spinning from tailshaft point both spin the same way.

Thanks

RX-747 · Postby **RX-747** » Mon Aug 06, 2012 3:04 am

Not necessarily, if it is a torsen LSD its likely to still spin opposite ways as a torsen diff needs some friction on both wheels which is why they get unsettled by ripple strips, etc. If it was a mechanical or locked diff then yes they would generally spin the same way.. Best way to check if it is a torsen is to either have one wheel in dirt and one on the road and accelerate hard, if you go no where it is most likely open but if you take of at a decent speed it is most likely torsen but this trick does not always work... Just try to do a drift if it switches to the other wheel and nearly throws you into a pole its open, if you can control it then its a torsen haha (P.S. the drift thing was a joke)

bootz · Postby **bootz** » Mon Aug 06, 2012 2:23 pm

As I understand it, you will only feel the torsen in tight turns.

hks_kansei · Postby **hks_kansei** » Mon Aug 06, 2012 3:30 pm

If you've recently swapped from an open diff to an LSD you should be able to feel a noticable difference when accelerating during a corner.

Depending on the age of the Torsen, and your driving style, you should feel the LSD.

Things like U-turns when under power, and gravel carparks, should be noticable. (My inside wheel shuffles a bit)

Bear in mind, the Torsen T2 has a pair of friction disc things on the side gears, and a sprung washer in the centre that gives it some pre-load.
As the diff is used the washer fatigues and the pre-load is reduced.

A brand new Torsen will still have most of it's preload and will be more likely to shuffle at low speeds.
An older one (with more KM) will have less preload and will be less likely to shuffle/chirp.

The actual bias part of the diff doesn't really wear much, so it will be fine for ages.

alexpav · Postby **alexpav** » Mon Aug 06, 2012 5:45 pm

Thanks all, I haven't actually put it in yet as i'm currently building the turbo motor for it

Just wanted to make sure what I got was an LSD. I think I have confirmed this! Cheers

hks_kansei · Postby **hks_kansei** » Mon Aug 06, 2012 5:59 pm

alexpav wrote:Thanks all, I haven't actually put it in yet as i'm currently building the turbo motor for it
Just wanted to make sure what I got was an LSD. I think I have confirmed this! Cheers

In that case, use the 100% infallible method.

Look inside the diff case.

Shine a torch through the holes on the side where the driveshafts will go.

If you see a metal bar going across the centre, it's an open diff.
If it's clear through the centre, it's likely an LSD.

Torsen view:
http://www.miataturbo.net/attachments/g ... 1342200507

In an open you'll see the bar with the arrow:
http://www.miata.net/garage/diffguide/17.jpg

93_Clubman · Postby **93_Clubman** » Tue Aug 07, 2012 11:16 am

On the T1 you can also remove the filler plug to confirm. Basically visibility into the diff centre after removing the filler plug allows identification, although slight rotation of the rear wheels by hand might be necessary to align with diff centre cutout (see bottom of following): http://www.miata.net/garage/vlsd.html

With the T2 being manufactured differently I'm not sure this still applies, but it might, although this should help: http://www.miata.net/garage/diffguide/index.html

93_Clubman · Postby **93_Clubman** » Tue Aug 07, 2012 12:13 pm

"The 1994 and 1995 Miata have a Type I Torsen, which is the traditional worm gear unit."

"The 1996 and 1997 Torsen is a Type II. This unit has a different design with the worm gears being replaced by three sets of drive gears that are mounted with their axes parallel to the ring gear axis. It is simpler and less expensive than the Type I to manufacture."

With the T1 it's the worm gears that you can see when you align the cutout with the filler plug. T2's cutout isn't as large which limits visibility, but these clearly show the difference:

TORSEN LSD Type 1.JPG

TORSEN LSD Type 2.JPG

Open 1.8 diff in comparison:

"We know this is a 1.8 liter because it has a pinion damper and stub shafts with four ears, each with a stud in it, but no extra ears in between. It is open, as also circled, are the spider gears. Later 1.8 liter halfshafts, after mid '95 are one piece - without separate stub shafts. So this is an early 1.8 liter [open] differential".

hks_kansei · Postby **hks_kansei** » Tue Aug 07, 2012 12:16 pm

93_Clubman wrote:With the T2 being manufactured differently I'm not sure this still applies, but it might, although this should help: http://www.miata.net/garage/diffguide/index.html

T2 centre looks like this:

So the gears won't be visible through the fill/drain plug, just the cast housing.

edit:
You've already replied with the same answer.

93_Clubman · Postby **93_Clubman** » Tue Aug 07, 2012 12:19 pm

And fortunately from the housing alone the difference is apparent when you know what the others look like.

johnnyreble · Postby **johnnyreble** » Tue Aug 07, 2012 12:25 pm

Hi,

Just in case anyone is interested, I bought an OBX Helical LSD off Ebay about $400 and it's awesome, works really well, I had it fitted by a profesional and he put new bearings in at the same time.

Johnny