Which style is better, obviously the S4 LSD can wear out because of the clutches, but I heard it reacts quicker than the fluid dependent torsen style S5 LSD's.

This car will mainly be used for autox and a few track schools.

 

I am not privy to 2nd gen diffs, but the tradeoffs between a clutch type and a torsen are the same. Clutches are usually adjustable (though you may have to be creative) since you can change the preload on the clutch plates. Clutches can sometimes be tuned with agents in the diff fluid. Clutches are usually lighter. Clutches do wear and have to be replaced.

Torsens are not adjustable. Torsens are heavy. Torsens do not depend on fluid; they are purely mechanical. Torsens usually can allow a higher slip ratio than a clutch.

 

I understand that the clutch type can release while your are braking and begining your turn in for a corner, which can unsettle the car. This will not happen with the Torsen.

 

Good info, so if you were choosing between the S4 and and S5 2nd gen diff, which one would you choose??

 

S4. I have a 90TII and Im rebuilding a S4TII diff. Ive also put in a S4 in my 86. The 86 one is worn out but both are 2 way. They shouldnt release when braking, those are 1 ways. Im gonna get rid of my viscous in a month or so. Note that any s4 diff you get is probally gonna be worn out unless it was properly broken in. My NA wasnt. My turbo seems tight. Well see soon.

 

Hmm...There's a S4 GXL diff at the junkyard, well the whole car is there, it's only got 80,000 miles on it. The yard also has a S5 TII, so I guess the S4 n/a LSD would be my best bet then, right?

Any way to check to see if it's worn out?

 

Hi
This is race car section, not street !!
Of course clutch type.
99+ stock FD has torsen type LSD.
But all the race cars swapped to clutch type LSD.
In Japan, Cusco bran new 2-way LSD is regarded to be the best one.

Thanks

 

Not sure what your talking since this car will be raced as I stated earlier.

Do you have any idea if the FD LSD unit will swap into the N/A rear end?

Also didn't the FD from 93+ come with the Torsen LSD?

Anyone know about the Miata torsen swapping into the N/A rear diff?

 

I would go with the clutch pack. I think the TII is alot bigger than the NA. Itll be a bitch swapping the FD into the TII. Plus youd have to find halfshafts and driveshaft. Im assuming you are going to upgrade the tranny also.

 

Goto solomiata.com. These guys kknow their shtuff. As far as I remember the the torsen unit will fit into a first gen housing with a bit of grinding and mods to the axles to fit the new spider gears, but am not sure about the fc. As well I think the clutch unit hooks up better but needs more maint. As I said check out the miata guys.

 

Good website, now I'm curious if anyone has real world experience swapping the torsen from the miata to the N/A rear end? I'm thinking the pinion shaft needs to be lengthened

 

The Miata Torsen is the unit of choice for a racecar. The mechanical worm gear nature of it allows you to get on the power sooner and accelerate harder out of corners with less wheelslip. It is not a traction control of any kind, but it allows a higher bias ratio between the rear tires while still providing maximum forward bite. In certain instances, the clutch type will cause an understeer condition because bias ratio is not as great. The car will "feel" a bit freer getting in and out of the corner with a Torsen, and may require a bit of fine tuning of your setup to optimize the handling vs. a clutch type, but is generally considered the faster of the two setups once everything has been maximized. You can buy them direct from Mazda Comp for, I believe, around $670. A used one will usually bring $400 or better.

The FD Torsens will not work as the ring gear diameter is greater than the NA.

 

The Miata diff should be a bolt-in. The only time a pinion shaft needs to be lengthened is when you use a non-stock gear ratio like a 4.88 or 5.12. Those gearsets are made for the FB rear end, so when using them in an FC, you must lengthen the pinion.

Changing the diff only would be totally different.

 

So could I just by the LSD unit itself and bolt it to my stock NON-LSD N/A diff? Or would I have to start out with a LSD diff?

 

I don't know that there is any difference between the two housings other than the little metal tag that denotes it as a LSD. Buy the diff and simply swap the new carrier in for the old. Now this is not a job for a weekend wrencher, so unless you feel totally comfortable and have the proper tools to check preload and set backlash, leave it to a professional.

The pinion gear will remain in the housing, but the ring gear will be transferred to the new diff. Not a bad time to replace the carrier bearings as well.

 

I didn't see anyone mention this.
But S5's do not have TorSen LSD's. They have Viscous LSD's (VLSD).

The advantage of VLSD (S5) over Clutch Type (S4), is that most FC'ds will have worn out clutchs by now (11 years old at least), and some say they wear as early as 30-50k miles. But I've read elsewhere that they should last to around 80,000 miles. The wear depends on how much you use/abuse your LSD, but those were just basic figures. No promises.

With VLSD you can just change the fluid and it will work like it should again.

Most would go w/ Clutch type if they had to choose for performance between Clutch LSD and VLSD.



I also have a lot of info on gear ratio swapping, and Miata Torsen swapping downstairs on my other computer, but have no way to post it on the forum :-\



P.S. This is a great new forum

 

Here in Oz most of the racers now go for the Guru Torsen as it is brand spanking new made from top quality billet material compared with the mazda comp cast one! As well the performance is better, we have found getting the power down much earlier through the corners etc.

 

All of the race cars in the CART (indycar) series us a Torsen diff as they are a superior design.

 

If the N/A and TII diff's are interchangeable, and the TII and FD diff's are interchangeable, then it's safe to assume that the N/A and FD diff's are interchangeable. I KNOW TII diff's are interchangeable with FD diff's.

 

TIIs have a larger diameter ring gear, therefore, they wil NOT interchange with the FC NAs.

Theoretically, I think you could swap in the TII complete rear end, but I think you would need the halfshafts and driveshaft as well. Then you could use the FD Torsen.

 

So I guess it would be best to use the Miata torsen then if I'm using the N/A rear end. I just need to find someone that's done it now to get the details...

 

Good stuff Chris...thanks for the clarification

 

Thats alot to chew on. Lets shift gears (sorry) How about my 85 SE, will the guru or mazda comp unit bolt in?

 

P.S. Hot new forum!

 

Hi Sorry, 85SE, is that Gen 1? If so yes, a direct bolt in, side gears on the Guru are supplied for all Gen 1 axle sizes.