Cool keep us updated I should have mine on hand in a couple of weeks.

I order the ring & pinnion today and should have it next week. So I hope to start the job on weekend of 21-23

I'm just posting this up here for my own reference. Amount of play allowed between ring and pinion is ~ .003"

Well got my torsen diff in a couple of days ago, ill post up the actual differences hopefully tomorrow

Cool. It will be interesting to hear your thougths on this...

I am also curious to how this works out. Mine is starting to go and has about 1.5" of play if measured from the outside of the tire.

I know it is only a matter of time...

Please keep us posted as well as where you got the parts.

Well the differential itself I bought from Jimmy at Fuji Racing, he was just received a sponsorship from Kaaz differentials so he'll be using those.

Now from my original understanding on the previous threads and what not is that you loose 12mm of contact area with the spline because they are in a little deeper into the casing of the diff.

This is not the case, the axle length are actually the exact same (so they bottom out in the same spot as the RX7 differential. Also the spline on the Miata Differential appear to be a little deeper into the hole, I'm taking about 1 or 2 mm so not much but every bit helps.

So the question I guess goes to be is that extra 10mm or so of spline really needed? I think if we factor in the fact that since these Miata diffs are a few year technologically ahead of the RX7 diff I think it will be fine. By that I mean the materials used, along with the treatment process could make the miata diff spline stronger than the RX7.

Also another thing to consider is that the in the rx7 rear end, I believe its already common knowledge now that the axles are the weakest link of the rear end, and if those are good for about 300HP or so, then I would have to say that the diff spline is way over engineered for the rest of the system.

One thing that I could see is if you're using the stock axles the splines on there might be even weaker now as all the torque is being applied to an even smaller area, but if you have a set of after market axles such as the Mosers that Re-Speed sells it should be fine from the strengthened material.

I'll post pictures of everything with measurements later on.

Forgot to mention the Miata pumpkin will bolt right into the FB axle housing. You will need to grind the housing down if you plan in keeping the watts link, but if you've replaced itcwith a watts linkbit will not interfear with anything. Just slap on the FB pinion flange and drive.

Ok, I just went to the track yesterday with the torsen on it. It worth all the money. It Still slide a little bit but you press the gas a the car just acelerate like the back to the future car. It doesn't spin the tire at any moment.

I took off 1.6 seconds of my previus time. But I was running potenza street tires in 195/60 instead of the Victoracer 205/50 and the car is a lot fun to drive.

In the end the car broke an axle and we end it towing the car to the mechanic. But we suspect that the axle was fragile from before. The mechanic mentioned that the axle did not look good.

Maybe it was the 10mm less of contact. The car is aspirated with about 160-170whp. But at the end of every heat we took a "cooler" lap and we take that lap a use to drif it. So we "abuse" aliitle bit.

I bet the time gained was mostly down to the tires.

As for the axle breaking, where did it break at? But it is like I suspected that the stock axles will break before the torsen . If you get the moser axles though I bet you'll be fine for years to come. Even the other guy there with the turbo charged car is running the moser axles. Everything in stock form, the axles will go before anything else in most cases.

I still need to post up the dimensions and pictures

Probably I will buy the mosler axle I'm waiting for the mechanic to told me excatly what happen and what will I need to purschase.

The 1.6 seconds was on the torsen. My old LSD wasn't working at all at I was spinning the inside tire so hard that I have to wait until the car was on the straigh line to really push it. Now I can hit the gas in mid-corner and no spinning. The street tires aren't bad but it didn't compare to the victoracer. I will try to put a street 225 tire in the back. The local rules only separate the cars between street and track tires for now.

Ok the axles are fine. The mechanic told me that the ring and pinnion have severe damage. I was wrong and the 10mm less of contact it wasn't on the axles it was on the ring and pinnion. Let see

Are the teeth gone on the ring and pinion? if it is it wouldn't be torsen related. If you said you twisted the splined area of the axles, that would more be torsen related. The ring and pinion could have been something as stupid as just not being installed properly. Were any of the bolts loose on the sleeves that hold the ring and pinion on? Keep us posted on all this, and pictures would be great.

You're 100% right the mechanic (he have a high experience on this) say that it was his fault and was very frustated. He have a good reputation working on rear ends and every one was alittle surprise of this failure of him. He repair it without cost to me and the car is running well again. My next Track day is July 18. Let me see if I can get a camera

Cool good to hear the update. Ya it happens to the best of us. But the real men admit to their mistakes.

Well finally had some time to get the whole thing done. I was going to take measurements of the spline to show the difference, but my caliper's battery decided to be dead.

One really interesting thing though, the stock differential weighs about 4lb more than the miata torsen unit. Thats a considerable amount of weight loss off the drivetrain, and should definitely help with going the rpm quicker.

Also in these pictures you can see the what the isotropic super finishing does to the gear set. Its for making the gears mesh smoother and thus reducing wear and helps by not increasing the heat of the units neither. And everything on the torsend one is used parts (minus bearings and seals) before there's any confusion that I bought a new set and polished it. The other gear set is what they normally look like from factory (but probably a bit cleaner than that)

Anyways, enough words, and onto the pictures:

https://www.rx7club.com/attachment.p...1&d=1283021785

https://www.rx7club.com/attachment.p...1&d=1283021785


https://www.rx7club.com/attachment.p...1&d=1283021785


https://www.rx7club.com/attachment.p...1&d=1283021785


https://www.rx7club.com/attachment.p...1&d=1283021785

A few more pictures:

https://www.rx7club.com/attachment.p...1&d=1283022121

https://www.rx7club.com/attachment.p...1&d=1283022121

https://www.rx7club.com/attachment.p...1&d=1283022121

https://www.rx7club.com/attachment.p...1&d=1283022121

If all goes well, I should have it in the car tomorrow or tuesday at the latest. I'll report how drive ability goes with it.

new one looks purdy!

i'm surprised at the weight difference...

I wonder how much the os giken weighs in comparison to both

Thanks for the pics and analysis dj55b


-Bern

subscribed :nod: my rear end has been wearing out it an 84 gsl-se, a bunch of inner tire spine out of corners and iv been trying to research what i am goin to replace it with before its not drivable lol iv been thinking about this miata swap for a while now. good info:icon_tup:

Out of interest the worlds leading circuit motorsport Formula 1 are using electronically biased clutch style limited slip differentials. Properly setup I believe a clutch system LSD is better for drag and circuit. Also out of interest neither type works with a wheel off the ground...

The only downside is a slight amount of clunking when doing very tight low speed turns with large amounts of torque (small turbo + u-turns). Also trailing throttle oversteer is a problem because the 2-way action tends to lock making the uncertain gen1 rear end even more-so haha. That said straight line on throttle stability is brilliant.

Hmmm, I wish I had weighed it. I have the stock one, but the Giken is in the car. I would venture to say that there is probably not much of a difference, maybe + or - 1lb. In the abover weighing example, the entire housing is being weighed and there can be some casting difference or maybe even slight housing changes from year to year (I'm not sure if they are the same years), or even weight differences between ring and pinions.

To properly know the weight difference of the rotating parts, the differentil itself should be weighed.

This is true, but the torsen unit itself is physically smaller than the stock clutch one. I'm going to try and get some weights from a few people. I have a stock one that I can just take out, and I think that I can get my hands on a used miata one.

I also believe one is a 3.9 and another is a 4.1 gearset, but I'll have to double check that and I don't exactly know if that fully makes a weight difference. I'll start another thread asking some gurus about the rear end weights.