Best Differential Swap

[bootz]

If you get the entire pumpkin(Front + Rear housing) then replacing the whole lot only takes a few hours. Personally I just took the whole pumpkin out, then dropped it into a diff specialist to get a 4.1:1 crown wheel /pinion and clutch pack LSD installed on my NB8B. Was $280 if I brought in the diff or $500+ if I brought in the car itself. I think i paid $190 extra to have all the seals/bearings replaced on top at the time as well.

From memory all I did was remove the lower control arm long bolt and pop out the drive shafts. Then rear subframe brace, 3 bolts on the PPF, pry the diff off the spacer in the PPF and 2 bolts to the subframe had it. That was over 3 years ago now but it's one of the easier jobs I've done on the car.

Thanks that is good advice. Can you tell me how the 4.1:1 travels on the road ?? - I am tending to go the whole hog and take the 4.1 torsen option but the 3.9:1 torsen 2 has also been highly recommended. They are pretty close, I'm thinking you could fine tune through tyre size.

Re the speedo, did you not bother or did you replace the sensor/pickup with an nb8a ??

[Hellmun]

You'll lose a little economy as you'll always be revving slightly higher but it's pretty minimal. I never bothered with the speedo change, it's wrong the right way so to speak. 122kmh is now 110 so as long as I adhere to the speedo past camera's I'm really safe. Car does feel a lot stronger on the track though which is where I noticed it the most. I found with a good intake and exhaust/ECU I started to get into a horrible spot at T10 at wakefield with the 4.1 as I was redlining just before the brake point and then also revving too high in 2nd gear and too low in 3rd gear. It was still lapping faster than it did with a 3.6 but I swapped to 225/50/15 tyres to fix this which let me use second through the corner and I clip the redline at the brake point. This was even faster again . Even on the street I think the 4.1 makes the car feel significantly faster and more fun. If I got another NB8B I'd put a 4.1 in again.

So I think you'd be happy with a 3.9 or 4.1 to be honest but it's easier to run a bigger tyre than a smaller tyre to adjust the final drive so I'd go 4.1. For a permanent street car get the speedo sensor though. Also in most restricted modification race series you can only run a diff ratio that existed for your model. In the case of NB's that's 3.6, 3.9 and 4.1 only so if you consider a 4.3 and might want to do some racing bear in mind that could put you in the unrestricted mod classes.

[bootz]

Both 3.9 and 3.1 ratios sound good.

So the big question now is do I go Torsen Type 1 or Torsen Type 2. Does not seem like there is too much info on the differences so they might be minimal.
Lots of fun the Mx-5.

[pcmx5]

If you were to buy a low klm diif with an LSD in either 3.9 or 4.1 you would be up for around $300 to have it fitted( thats what it cost me drive in drive out) so $1100 all up.If you use your current diff and change the ratio and put in a lower crown wheel and pinion remember you will have to factor in the purchase cost of both to Hellium's figures.His advice re using the tyres to gear up a 4.1 is interesting and he is right you can do that to alter a 4.1 to make it effectively slightly lower numerically in comparison to one with standard tyres but if the 3.9 wasn't what you wanted you would have to reduce tyre size or profile to get more low down punch.

Try to have a drive of some cars with these diffs if you can,may be someone nearby who has one will volunteer.Sorry but not really able to help with the effectiveness of Torsen 1 vs 2.

Peter.

[Guran]

So the big question now is do I go Torsen Type 1 or Torsen Type 2. Does not seem like there is too much info on the differences so they might be minimal.
Lots of fun the Mx-5.

According to Norm Garrett's book, the Type 2 has a higher bias ratio and is cheaper to build (so presumably cheaper to buy a new Type 2 versus a new Type 1?). The Mazda part number for Type 2 is MM02-27-200A. Might be worth having a search through the garage section at miata.net because I'm sure this has been covered plenty of times over there.

[bootz]

According to Norm Garrett's book, the Type 2 has a higher bias ratio and is cheaper to build (so presumably cheaper to buy a new Type 2 versus a new Type 1?). The Mazda part number for Type 2 is MM02-27-200A. Might be worth having a search through the garage section at miata.net because I'm sure this has been covered plenty of times over there.

Thanks Guran, I have been lurking there too often for my wallet.

The thing is if I don't shell out for an lsd I will always be wondering what it would have been like. Alternatively I might drive one and think Yuck! The joy of having options

[bootz]

If you were to buy a low klm diif with an LSD in either 3.9 or 4.1 you would be up for around $300 to have it fitted( thats what it cost me drive in drive out) so $1100 all up.If you use your current diff and change the ratio and put in a lower crown wheel and pinion remember you will have to factor in the purchase cost of both to Hellium's figures.His advice re using the tyres to gear up a 4.1 is interesting and he is right you can do that to alter a 4.1 to make it effectively slightly lower numerically in comparison to one with standard tyres but if the 3.9 wasn't what you wanted you would have to reduce tyre size or profile to get more low down punch.

Try to have a drive of some cars with these diffs if you can,may be someone nearby who has one will volunteer.Sorry but not really able to help with the effectiveness of Torsen 1 vs 2.

Peter.

Hi Peter, when you had yrs fitted was it the whole diff both housings, or just the centre with front housing assembly? $300 seems reasonable for a good job.

[pcmx5]

The lot and that is what you would get from MX5 Plus,undo the bolts that hold the diff in the housing after removing the shafts remove, replace diff and shafts.

They put new shaft seals in and obviously new oil and it was $300 from memory or may have even been cheaper,I will try and find the reciept.

In the NC it was a bit harder as they had to remove more bits to change over (again complete diff) including dropping the exhaust and that cost me $380.

Peter.

[bootz]

Thanks for all your advice guys, most helpful. Happy holidays.

[bootz]

I wonder why Mazda chose the 3.6 diff for our six speeder???
Every other market uses the 3.9
Maybe it was a political decision re: fuel consumption and emissions. Marketing??

[RawSouth]

I was looking at buying a TorSen a little while ago (in fact I still am, but Im trying to be good and save some coin). From what I read at the time. In terms of strength,

T2 > Super TorSen > T1.

Occasionally good deals come up on ebay too, so thats worth keeping an eye open for.

Josh

[Regie]

I was looking at buying a TorSen a little while ago (in fact I still am, but Im trying to be good and save some coin). From what I read at the time. In terms of strength,

T2 > Super TorSen > T1.

Occasionally good deals come up on ebay too, so thats worth keeping an eye open for.

Josh

i got my T2 off ebay for $200

[bootz]

OMG that is cheap
what diff ratio are you running, stock 3.6 ?

BTW the Elise seats are sweeet!

[RawSouth]

Yeah, I wish I could get one for $200. Id buy one in seconds!

[93_Clubman]

Not sure about the 10AE having a 3.9,there were claims and counter claims re that on this forum over the years.

Mazda spec sheet for Australia indicates 10AE in Australia is 3.6 (3.9 in US though):
viewtopic.php?f=18&t=43268&start=15

Also Slowpoke has a 3.6 CWP in his shed out of his 10AE after he had the 4.1 CWP fitted - he's the 2nd owner & bought his 10AE with 6.9k kms on it.