How To: Swapping miata torsen LSD into N/A FC diff housing
 

Well, while I am doing this for myself, I decided to make a write-up for anyone esle that may be interested in doing this. First off, I would like to say that I am by no means an expert, so if anyone has any comments or anything else they would like to ad, you are more than encouraged to do so. OK, so lets get started. First well take a look at the 94+ Miata rear end. You will see ten 12mm bolts circling the outside of the diff. You will start by removing these bolts.
http://www.imagestation.com/picture/...6/fbb93d8f.jpg
Once the differential is open, this is what you will be looking at. You will then continue by removing the four 12mm bolts that hold down the bearing guides, as well as the 10mm bolts on the top of them
http://www.imagestation.com/picture/...f/fbb93d91.jpg
After that is removed, the LSD and the ring gear will pull right out. This is what you will have
http://www.imagestation.com/picture/...c/fbba67c2.jpg
Now you will be removing the ring gear from the LSD unit. It is held on by the ten 14mm bolts on the outer ring of the LSD. You will need an impact gun to remove these, they are on there extrodinarily tight. Once you have unbolted all ten bolts, the ring gear will be able to be removed from the LSD unit. You will mst likely need to tap it off with a hammer (gently) as it is a tight fit. Once you have removed the gear, this is what you will be left with.
http://www.imagestation.com/picture/...7/fbb93d8a.jpg
Now, you will repeat the process exactly for the FC differential. Once you get the ring gear off of your old FC Limited slip, it is time to install it onto the miata torsen LSD. Just slide it on, and torque all of the ten 14mm bolts down to the proper spec, and in proper sequence (can be found is FSM) Now you will have your FC ring gear onto the Miata torsen LSD. Now, its time to re-install the LSD into the FC housing. If your bearing guides and caps have become seperated, like this
http://www.imagestation.com/picture/...d/fbb93d86.jpg
they will need put back together. The bearing guide slides inside of the cap, and the outer holder then threads into the side of the bearing retainer. It should look like this when together
http://www.imagestation.com/picture/...2/fbb93d84.jpg
Now that you have the empty FC housing
http://www.imagestation.com/picture/...9/fbb93d82.jpg
Its time to set in the torsen LSD and your FC ring gear assembly. Set in in place so that the bearing guides line up, with the bearing being inside of the retainer, and you can bolt it down to the proper spec.
http://www.imagestation.com/picture/...2/fbb93d7c.jpg
Now would be a good time to get a new gasket , or silicone the differential housings, and then reinstall the two pieces of the housings back together, and you are done!
http://www.imagestation.com/picture/...b/fc6321a4.jpg

Great job.:D

How much did you pay for the Miata LSD?

Same question......how much?

I happened to get it out of a wrecked Miata, but expect to pay ~$150-$200 for on the parts trader or Ebay.

whats the advantage of doing this?

for some reason I am only seeing red Xs

But great write up other than that

The advantage is that torsen is an immediate lock-up LSD, whereas viscous can take a bit of time to lock up, and clutch type can wear out. And about the pics, can everyone else see them?

I saw them the first time, didnt the second when i read Icemarks post, but I see them now.

I hate the internet.

BTW- what are S4 GXL LSDs? Clutch type Im guessing?

will this procedure work on an N/A diff that didn't originaly have an lsd?

So what are you doing with the old fluid type LSD???

excellent writeup! maybe this will be another thing i will do over winter..

where can i find specs on a miata LSD (ratio, etc? that changes along with the new internals right)? how will i know i've found exactly what i need? this works on any s4 diff? or just the LSD from an s4? :)

The gear ratio doesn't change, that is why you remove the old ring and put it on the new diff.

The miata ring and pinion are the wrong lengths and sizes to use in the FC diff. assembly.

But will it work on non LSD S4's?

http://cgi.ebay.com/ebaymotors/ws/eB...ADME:B:LC:MT:1

:D

This I am not 100% sure of. Id have to take a look inside of the open diff and see, but I would assume that it would be the same.

ah man, bummer- ebay

hey how much to ship it too me in CA (94931) if I win the auction?

And drago, yes it would work in all FC N/A diffs regardless of series

So... TII people can only use the FD torsen or is there another car we can get them from... I know one can buy them new but $150-300 is better than $800!!!

wow the FD torsen fits in the TII

superb write-up... I knew it could be done, but never saw a full write-up on the topic until now. Will be glad to find this in the archives next summer when I'm ready to put an lsd in!!

would this work in a S5 diff?

Well done. Nice you included the pics. Now I'm looking for a junk miata.

btw: how's the lsd setup feel?

I havent had a chance to re-install the diff yet, so I dont know how it feels. Hopefully good ;)

And 2a+Ron, yes any N/A FC diff it will work in, the picture is actually a S5 diff that I am swapping it into (GTUs to be exact...4.3 + torsen, oh yea :cool: )

so us turbo guys are sol?

Great write-up!!!!

As said before, the procedure will be the same, but you would need the torsen from an FD.

And also on more thing that I had failed to mention. In the FSM it calls for you to set the backlash. I personally dont have the appropriate tools to do this, so I basically tried to eyeball it and make sure everything was level. (yes, I tried to eyeball .1mm..:rolleyes: ) So I will report back if I have any problems...