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Old 01-18-2007, 02:09 AM   #1
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I am a new miata owner and I was wandering if mine has lsd or torsen or just open. I jacked up the car in the rear and rolled one wheel forward and the other one did the same. So I was wandering if that means I have limited slip or a torsen?
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Old 01-18-2007, 02:19 AM   #2
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the torsen IS the LSD rear end, the other model is the open diff.

the only other LSD thats not a torsen are those from the 90-93, the 1.6 cars...they have a viscous(sp?) vlsd 6" or a open 6". The torsen lsd is from 94+ in the 1.8 car and is a 7" and they also offer the open in 7" for those years...not sure how to check.
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Old 01-18-2007, 02:33 AM   #3
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Originally Posted by nightrider1992 View Post
I am a new miata owner and I was wandering if mine has lsd or torsen or just open. I jacked up the car in the rear and rolled one wheel forward and the other one did the same. So I was wandering if that means I have limited slip or a torsen?
If both wheels spin the same way you got an LSD, if you have 89-93(1.6l) then it's Viscous LSD, if it's 93+(1.8l) then it's a torsen, but might be something aftermarket too.
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Old 01-18-2007, 03:35 AM   #4
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SWEET! Thanks guys.
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Old 01-18-2007, 09:43 AM   #5
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RusMan, I don't think that is correct. I have read many accounts that a Torsen CAN spin wheels in opposite directions, as well as sometimes not spining both at all.

One way to check is by jacking the rear and see if you can turn both in the same direction, it should prove to be difficult (If you can turn them both the saem direction, then no torsen). However, I don't believe the Viscous (89-93) can be checked to do the same.

The easiest way is calling Mazda's 1-800 number and giving them your VIN.
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Old 01-18-2007, 11:58 AM   #6
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The stub shafts on the 90-93 viscous are different than the 90-93 open diff. www.solomiata.com will tell you if there is a way to do a visual inspection on the car.

Really on the 90-93 cars the viscous diff isn't really all that great when new and most likely worn out on a 15 year old car and might as well be open. I've got one on my car and can tell no real difference between it and the open diff.
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Old 01-18-2007, 12:05 PM   #7
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Yeah I jacked it up last night and turned one of the wheels and the other did the same, so I am thinking that it has the viscious lsd in it. I was playing around in it the other night and was cuttin some donuts in it and I thought it felt like it had one, but I guess I will give them a call and find out.
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Old 01-18-2007, 12:19 PM   #8
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Viscous LSDs are less efficient than mechanical types, that is, they "lose" some power. They do not stand up well to abuse, particularly any sustained load which overheats the silicone results in sudden permanent loss of the LSD effect. They do have the virtue of failing gracefully, reverting to semi-open diff behaviour, without the graunching of metal particles / fragmented clutches. Typically a visco-differential that has covered 60,000 miles or more will be functioning largely as an open differential; this is a known weakness of the original Eunos Roadster. The silicone oil is factory sealed in a separate chamber from the gear oil surrounding the rest of the diff. This is not serviceable and when the diff's behaviour deteriorates, the VLSD centre is replaced.
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Old 01-18-2007, 12:27 PM   #9
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I have a 94' 1.8 non-torsen mx-5, just the (european) open diff..will the mazdaspeed 90-93 lsd (goodwinracing.com) drop in just as well or should I get an rx7 clutch type lsd? thanks
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Old 01-18-2007, 12:29 PM   #10
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no, 90-93 guts are not interchangable. You can buy a Torsen LSD unit and drop it in set the backlash and be done. Or go with an rx7 clutch-type, but need to upgrade to 99+ halfshafts.
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Old 01-18-2007, 12:29 PM   #11
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crap
rx-7 it is then..
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Old 01-18-2007, 12:31 PM   #12
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find a torsen lsd meatball, there's a bunch on m.net and ebay.
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Old 01-18-2007, 12:43 PM   #13
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didn't see your edit..
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Old 01-18-2007, 01:26 PM   #14
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Originally Posted by braineack View Post
Viscous LSDs are less efficient than mechanical types, that is, they "lose" some power. They do not stand up well to abuse, particularly any sustained load which overheats the silicone results in sudden permanent loss of the LSD effect. They do have the virtue of failing gracefully, reverting to semi-open diff behaviour, without the graunching of metal particles / fragmented clutches. Typically a visco-differential that has covered 60,000 miles or more will be functioning largely as an open differential; this is a known weakness of the original Eunos Roadster. The silicone oil is factory sealed in a separate chamber from the gear oil surrounding the rest of the diff. This is not serviceable and when the diff's behaviour deteriorates, the VLSD centre is replaced.
I own cars with all three types of LSD's (viscous, torsen, clutch). And I use all of them for either autocross or rallycross (some do both).

Viscous LSD's are not fragile at all. I challenge you to try and destroy one. If you overheat one or have too much spin on one wheel the plates spinning in the fluid will actually touch and try to lock the diff. This is called "humping". My DSM has a viscous center and rear diff and is making 300+HP. I've beat the s**t out of that car for rallycross and there is a LOT of wheelspin even with grippy dirt tires. They still work just fine even though I abuse and overheat them regularly. I would know immediately if one were to fail and either go open or locked. With a VC both wheels will turn the same direction if you jack up the car and turn one. If you hold one of them still (in neutral obviously) it will take some effort to turn the other one, but you won't get a 'breakaway' feel like from a clutch. It will just offer smooth resistance in proportion to how fast you try to turn it.

I autocrossed our turbocharged miata for 2+ years with the torsen. There is no LSD effect with the car jacked up since it's a torque multiplier. You can tell it from an open diff by pulling the axles and looking through the diff. If you can see through the diff then it's a torsen. If there's a shaft going through the center then it's an open. The torsen is a very good diff as long as you don't lift a wheel off the pavement. As soon as either wheel leaves the ground it's an open diff. Power transfer with a torsen is smooth and seamless and it works the same wether you're turning or going in a straight line. I was told the torsens were indestructable, but I managed to destroy mine FWIW.

I replaced the busted torsen with a CUSCO Type-RS 1.5 way clutch type. I replaced it last season and autocrossed our WRX instead so I've not had it on the track yet. The clutch types have a significant amount of preload and tend to resist low-speed turning. It takes significant effort to get the rear wheels to turn opposite directions with a clutch diff. From street feel alone it wants to act like a drift car, but slides are a lot easier to control than with the torsen. I'll get a feel for the car this season with some sticky r-comp tires but I may end up dropping the pre-load on the clutches if I get too much oversteer.
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Old 01-18-2007, 05:15 PM   #15
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The S5 RX-7 Turbo II's and Z32 300ZX turbos used viscous LSDs with no problems.

Nightrider1992: To determine what you've got, all you need to do is look at the flanges on the stub-shafts coming out of your diff. If the edges are symmetrical, then it's an open diff.
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Old 01-18-2007, 10:29 PM   #16
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Quote:
Originally Posted by Brian View Post
Nightrider1992: To determine what you've got, all you need to do is look at the flanges on the stub-shafts coming out of your diff. If the edges are symmetrical, then it's an open diff.
Damn, somebody beat me to it.

Seriously though Night, assuming you have a '92 from your username, it truly is that simple. Here's a link to a page that shows you what to look for:
http://www.miata.net/garage/diffguide/index.html

It's about 1/3 down the page, the picture with the heading that says:
"1.6 liter finned case VLSD. We know it's a VLSD because the left side stub shaft flange has the ears shown."
Two down from that is a picture of an open diff. What you're looking at is the side of the differential where the CV axles bolt to. (the half-axles that drive the wheels.) If your flanges look like the ones in the picture then you have a viscous limited slip differential. It's a different mechanism then a Torsen, but essentially the same outcome.

People with '94 or later cars (or those who've put '94+ diffs into their 1.6 cars) have it harder- there is no way to tell definitively without removing something. I find that it's not impossible to look through the oil fill hole while shining a really tiny flashlight in there, but you might have to pull the muffler off to get a good look. And you have to know exactly what you're looking for. It's hard to describe.

When I bought a 1.8 diff out of a wrecked '95 last year, I got the VIN number and called Mazda USA's customer support line. They were able to tell me that the car in question was an "M" edition with a 5-speed, and from browsing the old brochures it came to pass that all '95 M's with 5-speeds had LSD's.
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Old 01-19-2007, 03:51 PM   #17
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Mmmm.....acid.......


Oh ****..nvm....sorry.




Is your diff housing smooth or finned? Smooth - open, finned - LSD. Only works on 98-93 cars, the 94-97's are all finned, as I've had a torsen and an open both in finned cases.
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