Question about older cars and differentials

[Oilleak]

Hi guys,

I am trying to figure out what kind of rear end the Miata that's sitting in my garage has.
it is a 1990, and I am not sure if it has the optional V-LSD on it. There is no physical way to tell by looking at it.

What's the adventage of having a VLSD over an open diff (which I suspect that I have) for city driving / cone racing on the weekends?

Many fanks.

[kwando]

the resident miata expert is willerickson... he owns 2 of them and a yaris

[WillErickson]

Well, I'm pretty sure Greg will have something clever to say about "Miatas" and "rear ends", but here you go: http://www.miata.net/garage/diffguide/index.html

[WillErickson]

Some more info here: http://www.miata.net/garage/vlsd.html

[Oilleak]

Hey there, thanks for the input guys.

I've checked Mx-5's garage - and the picture of the diff's made my head "ASPLODED"!
Without taking the diff apart, is it safe to say I only have an open diff and no VLSD?
As well, how does it affect me when I am doing city driving / vs. chasing cones on the weekends?

[WillErickson]

Easiest way is to call mazda (800-222-5500), give them your VIN and they can tell you how the car was equipped from the factory.

[Oilleak]

I will have to wait until tomorrow :(


What year are your Miata's Will?

[WillErickson]

93 and 94, the 94 has an FM2 turbo, both have hard dog roll bars and FM suspensions. The 93 was my dd until recently.

I'm not cool enough to drive an S2000...

[Oilleak]

I've called MAZDA CSR twice now, and they've promoised they will email me the report of the car (list of options etc). I've been waiting for 25 hours now, still no email on 2 email accounts from them.

I think I am just going to test the diff on the snow today :)

[repiv]

I think I am just going to test the diff on the snow today :)

Assuming that the diff is not broken, that's probably the easiest way to test to see if you have some sort of LSD. On a viscous type limited slip, it will have a clutch pack. From past experience, clutch pack LSDs tend to lock up with a "clunk" when one drive tire is on slippery ground. Torsen type (worm gear) seem to be more progressive when they lock up. However, if both drive tires are on evenly slippery surface, you may not be able to tell at all.

[dc_35]

a torsen type lsd can act a lot like an open diff in 0 grip conditions

[CoralDoc]

If you have a viscous LSD in your car, it's probably not LSing anymore. The advantage of a limited slip differential is that it puts power to the wheel with the most grip. The S2000 and later Miatas (1994-2005) have essentially the same design Torsen unit. It works great until one of the wheels becomes unloaded (or nearly so), and then it acts like an open diff. Clutch-type LSDs can be made to be very progressive and will still funtion well with one unloaded wheel.

If you have an open diff in your car and want a limited slip, your best option is to update to a Torsen differential from a 1999 and newer Miata with 5-speed transmission. That will preserve your peppy 4.3:1 rear axle ratio and give you a reliable and functional LSD. You will also need to change to the later model driveshaft and half shafts. I just did this conversion in my 1993 and it's pretty straighforward. The going rate for all of the used parts is around $1k.

Another alternative is to install a MazdaSpeed LSD (friction plate design) in your existing open diff. The unit costs about $750 and it will need to be installed and set up properly. The labor and parts (seals crush tubes, gaskets, etc) will drive the price up to aboutthe same as the Torsen conversion. I had a friction plate LSD in my car for a couple of years, and in that time, the platres wore enough to need a rebuild. The Torsen will never wear out (unless you break it with force-inducted power).