Tire spin--Torsen solution?

[Swingwing]

I'm looking for a way to tame the wheelspin I get--other than shifting at 1500 rpm!! I have a 99 Touring with the BRP/Stageone kit, 95mm pulley, and PCPro, so I'm making good power, but not ungodly amounts. I also have the base suspension, Toyo T1R 205/50/15s, and a standard diff. I think one culprit is the roads here in S. Dakota--the city never sweeps the sand off after storms, so the roads always feel loose. If I shift at 1500 I'm ok, but if I get a little agressive, I'll spin the tires, especially starting out on a turn from a stop. If I go WOT, I'll get lots of spin, little acceleration, and the car will fishtail in second and third gear.

So I'm thinking the answer may be swapping in a Torsen LSD from a junked Miata. Has anyone here ever done this swap?

Planetmiata (http://www.planetmiata.com/01-05_pricing.htm) sells a "Rear Diff Swap Kit 1.6 to 1.8 - 4.10 torsen" for $1100 (includes diff, driveshaft, alum. housing & cv axles). There are 4.30 and 3.90 swap kits for $1300. Finally, they also have a "99+ 3.9 [or 4.3] REAR DIFF (TORSEN)" for $900. Does having the entire axle make the swap easier vs. just swapping the differential?

Lucien

[snakebit]

It should help. It'll also help kick the rear around in turns.:biggrin:
I have the Torsen and often spin and wheel hop from a standstill. Next set of tires will be 205s.

Can't help you with the conversion. If you have a choice, a taller final drive should help too.

[Tom @ Fast Forward]

Yep. The Torsen is a definite help. I run 225/50-15s as well.

[pumpkin]

I don't see why you'd need new axles. You've got to pull the axles out of the diff to remove it anyway, so there's really no need to put new axles in. I did replace the axle seals, however, when I did my swap.
JD

[lds2002black]

The Spec Miata guys with the 1.6 cars are allowed to upgrade the diff in the 1.6 cars to the diff from the 1.8 cars and these look like the parts required to do that swap.

[ScottA]

I see there are two types of torsen diffs used in Miata's, a type I and a type II. I know that one has a diiferent load to traction ratio but I don't know which is which. Does anyone know which is the better between the two ?:confused:

[Tom @ Fast Forward]

I thought there were actually three? Oil coupled, clutch coupled and gear coupled in that order? In any case, you want the latest version gear drive. That is the one from 99(?) and newer that seems to take a LOT of punishment.

[ScottA]

There are actually two types of the gear driven diffs made by Torsen . They are of the same type of construction ,[ gear driven ],But one has a higher load bias ratio. I just was asking which one is the preferred one. I have seen both for sale on JDM parts sites, and both were used by Maza in certain year models.:confused:

[Tom @ Fast Forward]

Hmmm. I was not aware of that. All diffs have a ring and pinion. I thought the difference was the drive/connection to the axle shaft? The latest version is connected by gears and the older version was viscous coupled. ie. fluid/oil coupled. There was also an older version that had a clutch to couple the diff to the axles.

Here is everything you ever wanted to know about Miata Diffs. The VLSD (Viscous), clutch typ and type 1 and type 2 gear version. I would imagine the type 2 is the desired version as people always try to get them from the later model Miatas.

http://www.miata.net/garage/vlsd.html

[tann3r]

for all your miata differential needs

http://members.aol.com/solomiata/MiataVLSD.html

[Tom @ Fast Forward]

That is a little more up to date than the one on mnet. I think this is probably the answer he was looking for?


(Q)Is a TypeII better than a TypeI Torsen?

(A)No. They have different charactoristics but one is not stronger or better than another. The TypeI is designed to put out more bias on acceleration and the Type II is designed to have subdued acceleration bias and a stronger bias on deacceleration. i.e. The TypeII is more forgiving with trailing throttle.

[ScottA]

Thanks everybody !!!!
That was the info I was looking for. Appreciate the help.:biggrin:

[Swingwing]

OK, so it looks I just need to get the differential (4.30 ratio for the 5-speed) and swap it in. I've read I should also replace the differential bearings while I'm in there. Anything else?

Also, the swap doesn't seem too complicated, but any good walkthroughs out there?

[Tom @ Fast Forward]

If it were me, I would get something taller than 4.3. Either 4.1 or 3.9. with good boost/torque you can support it.

[MX-Drew]

Also while your there replace all oil seals and bearings, they are not expensive so now is the time to do it.

[Swingwing]

Tom,
Benefits/drawbacks of going to a 4.1?
- lower (probably more accurate) speed reading at any given rpm
- slightly slower acceleration

[Tom @ Fast Forward]

With all the instant torque supplied with a Coldside, first gear can run out pretty quick. I stepped my 6 speed from 3.6 to 3.9 diff gears and don't regret it one bit. I cruise down the highway at about 3600 RPM at 80 MPH and it still feels like it coule bear one more gear change. :)

My 6 speed is close to your 5 speed for 1-5 and 6th is a real overdrive. However, if I had a 5 speed, I would like the gears to be spread out just a bit more. 4.3 to 4.1 would probably be a good choice. Not too much and not too little.

The key with first gear is simple. A stock 1.8L Miata makes about 35 ft-lbs at 1000 RPM with a peak torque of about 70-80 ft-lbs. A Coldside 200WHP kit makes about 150 ft-lbs peak but makes close to 140 ft-lbs across the board. The transmission was designed to match the stock engine HP/tq curve but with all that low end torque, the gears can be taller and run out a few MPH more between shifts with no problem.

That is just my opinion. If I had it all in the car already I would probably leave it alone but you are looking to swap the diff out anyhow to get the LSD. Doesn't cost anymore to up the gears.

One caveat though. Don't swap out the flywheel for a light one if you are going taller diff gears or heavier clutch. First, the Coldside precludes the nead for a light flywheel. Those are great for stock engines and turbos but there is no torque problems with a Coldside. Second, Having that mass in motion helps overcome the problem of getting started from a dead stop. That problem is exacerbated by a heavy clutch or a taller first gear (diff). If it is a street car, leave the flywheel alone. If it is a track car, do as you wish because there is seldom stop and go traffic on the track. :)

[Swingwing]

Also while your there replace all oil seals and bearings, they are not expensive so now is the time to do it.

That would be the differential bearing and seals, not the pinion bearing & seals, right?