Any idea what differential this is?

roninsoldier83 · Postby **roninsoldier83** » Mon May 23, 2011 9:14

RX-7 Chris wrote:I think the VLDS out of the 84-85 rx-7 also fits but you may want to do a little more research on what that takes.

Do they have 4.30 gears? Direct bolt-on or does it require axles/driveshaft as well?

I'll look into it.

Postby **RX-7 Chris** » Mon May 23, 2011 9:14

They don't have 4.30. GSL came with 3.9 and GSL-SE came with 4.10. The stock axles should work but I think the driveshaft flange is different.

You can look at my car and compare if you want.

roninsoldier83 · Postby **roninsoldier83** » Mon May 23, 2011 9:14

RX-7 Chris wrote:They don't have 4.30. GSL came with 3.9 and GSL-SE came with 4.10. The stock axles should work but I think the driveshaft flange is different.

You can look at my car and compare if you want.

Not supposed to change FD gears in STS.... I think I'll just wait on a Miata VLSD as it's a direct swap (leave stock driveshaft & axles in there) and keeps the factory 4.30 gears.... trust me, the gutless wonder 1.6 needs all the gearing it can get haha!

ecam8000 · Postby **ecam8000** » Mon May 23, 2011 9:14

Couple things; I have a Torsen, and in the air it acts like an open diff. With the car idling in 4th (in the air) I can stop on of the wheels with my shoe. On the ground, one side on dirt the other on pavement, both tires spin. A limited slip (clutch pack) will not spin in opposite directions when the car is in the air (unless the clutch pack is toast).

On the other side of the coin. If I had a NA Miata, I would be looking at STS. It sounds like this is a great class for your car. Saturday, did you ever loose forward bite because the inside tire roasted? Sway bar adjustments and suspension settings can do wonders to minimize spin. If you are not having issues with one tire burn outs, the LSD is not really needed. The tires you are running are helping that. Some hard all seasons may need that LSD!

roninsoldier83 · Postby **roninsoldier83** » Mon May 23, 2011 9:14

ecam8000 wrote:Couple things; I have a Torsen, and in the air it acts like an open diff. With the car idling in 4th (in the air) I can stop on of the wheels with my shoe. On the ground, one side on dirt the other on pavement, both tires spin. A limited slip (clutch pack) will not spin in opposite directions when the car is in the air (unless the clutch pack is toast).

On the other side of the coin. If I had a NA Miata, I would be looking at STS. It sounds like this is a great class for your car. Saturday, did you ever loose forward bite because the inside tire roasted? Sway bar adjustments and suspension settings can do wonders to minimize spin. If you are not having issues with one tire burn outs, the LSD is not really needed. The tires you are running are helping that. Some hard all seasons may need that LSD!

Interesting info about your torsen. Although, based on looking at numerous pics & reading through quite a few descriptions, it is definitely a 1.6 open diff.

On Saturday, the inside tire did give up a couple times, most notably on my first run; on subsequent runs I kept my foot out of it until later in the corners to avoid spinning out. Going to take a while to get out of the AWD-spoiled habit of getting on the gas early coming out of a corner. Looking forward to working on it.

It's kind of funny, my urge to turbocharge the Miata was diminished a bit on Saturday... partly due to wanting to get better at driving the machine at this level, and the fact that I now know it doesn't have a 1.8 torsen in it further strengthens my want to leave it alone to an extent, as I think STS could be a class I could really grow in.

With that said, on top of looking for an OEM VLSD (legal in STS), I won't lie, I contacted Justin Mitchell regarding building me a STS legal MS-II ECU. While more power won't cure my lack of piloting ability over the car, at the same time, I'm a tuner at heart and really want to play with mid-range timing & AFR's in hope that I can make this thing a bit more responsive in the low/mid range to avoid having to shift down into 1st exiting tight corners.

Either way, it should be fun.

erod550 · Postby **erod550** » Mon May 23, 2011 9:14

Also be careful buying an old used VLSD unless they have tested it. I have read quite a lot of people have VLSD that doesn't work anymore for one reason or another. So it just acts like an open diff.

roninsoldier83 · Postby **roninsoldier83** » Mon May 23, 2011 9:14

erod550 wrote:Also be careful buying an old used VLSD unless they have tested it. I have read quite a lot of people have VLSD that doesn't work anymore for one reason or another. So it just acts like an open diff.

I've been reading a few different theories behind this, and like many of the other guys on Miata.net I'm not so convinced, as from what I understand the VLSD's need to heat the fluid to a certain level in order to become functional per se, the "put it in the air & spin a tire" test isn't really applicable for them, a bit harder to test.

Either way, I figure if I find one for dirt cheap, I can always swap it in there and sell the open diff that's on there to recoup the funds. Not a whole lot to lose per se. We'll see.

ecam8000 · Postby **ecam8000** » Mon May 23, 2011 9:14

Just to add a little bit. Even with my overwhelming additional power from my 1.8 (HA!) I have never spun a tire leaving a corner. I have spun the car many times though.

roninsoldier83 · Postby **roninsoldier83** » Mon May 23, 2011 9:14

ecam8000 wrote:Just to add a little bit. Even with my overwhelming additional power from my 1.8 (HA!) I have never spun a tire leaving a corner. I have spun the car many times though.

All hail the power of the mighty 1.8L!!

Honestly though, from what I understand about diffs, it makes sense that your car would behave the way it does. Both a torsen LSD & viscous LSD are defaulted to being "open" per se, unlike a clutch type diff. A torsen diff increases the amount of lock it has in a linear fashion based on the amount of force applied (torque), whereas a VLSD's not-as-useful locking function is increased based on the heat of the silicone fluid within the diff, not nearly as linear, or pronounced (doesn't offer as much lock as a torsen).

As such, I'm not too shocked that your torsen acts like an open diff in the air without a significant amount of torque being applied. In our low-power applications, I would think your torsen would work pretty well though.

roninsoldier83 · Postby **roninsoldier83** » Mon May 23, 2011 9:14

I found a VLSD online for dirt cheap, so I just went ahead and ordered it. I figured I can sell my open diff to help recoup costs, so I might as well, as I would essentially pay very little for it with the sale of the open diff. We'll see.

Any idea what differential this is?

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