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Differences in FC differentials

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Old Sep 12, 2013 | 01:56 PM
  #1  
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From: Chalmette, LA
LA Differences in FC differentials

I know that there are several different output shafts and that when you swap the turbo tranny in you need to swap the driveshaft/dif/axles.

I have an S4 N/A car with a welded open dif installed, I have a reshimmed S4TII chunk and output shafts that i want to install but dont want to put it in the N/A housing because I've read they are weaker and I plan on going turbo or LS so I want to get rid of it now. My questions are:

Do I have to install the S4TII chunk into an S4TII dif or can I use an S5TII?
and
When i swap the TII dif into my N/A car do I need the TII driveshaft?
and
Is there a way to identify what dif housings are what?

THANKS!
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Old Sep 12, 2013 | 05:18 PM
  #2  
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your question has just been asked recently(twice if I can recall correctly) so please look in this section.
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Old Sep 12, 2013 | 05:28 PM
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From: Tejas
from the Q&A thread:
Can I install the Turbo II transmission into an NA?

Certainly. But you need to also install:
-TII flywheel, clutch, pressure plate
-TII slave cylinder
-TII starter
-TII driveshaft, differential, axels
-Adapt the wiring.

MazdaTrix makes a TII transmission to NA rear end driveshaft, so if you don't want to swap your rear end, you can use that shaft instead.

Did my 2nd Gen RX-7 come with a Limited Slip Differential?
Only the following USA model 2nd gen RX-7s had a LSD from the factory:
86-88 GXL
87-91 Turbo
88 GTU
89-90 GTUs (however not the 89-90 GTU
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Old Sep 13, 2013 | 06:19 PM
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Yea I read all that, twice.

That doesn't really answer my question. If I have a NA tranny will the TII driveshaft work? That only talks about maying a TII tranny to a NA differential.
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Old Sep 14, 2013 | 08:39 AM
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no, the n/a tranny spline is smaller than the turbo tranny spline.

Last edited by misterstyx69; Sep 14, 2013 at 09:49 AM. Reason: no coffee.wrong place to reply.
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Old Sep 14, 2013 | 09:48 AM
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Dave is right.
The output shaft of the N/A is smaller,so if you try to put a TII Driveshaft in,it will not fit...same with the N/A into a TII,it just won't go!
If you get the Driveshaft FOR the transmission then it's all good.it will fit.
You can always look here to get a conversion shaft already made for what you are doing.: Driveshafts
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Old Sep 14, 2013 | 12:48 PM
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Ok well then I should be able to use the drive shaft I already have, I'll just swap the NA pinon flange onto the TII diff.
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Old Sep 14, 2013 | 01:51 PM
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It will not fit as far as I know,
That is why the guys that do this mod on the cheap just elongate the holes on the driveshaft.
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Old Sep 14, 2013 | 03:55 PM
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From: ontario
Misterstyx69 is right.
Flanges are a different size also, I just finished a n/a trans to tII trans swap, n/a rear-end, and after a lot of wasted time and reseach bought a mazdatrix driveshaft($300) with replacable u joints. Bolted in smoothly, peace of mind.
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Old Sep 15, 2013 | 11:33 AM
  #10  
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Yea I'll probably just elongate the holes haha. I'm cheap.
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Old Sep 17, 2013 | 02:03 PM
  #11  
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I have a new twist on my question:

I was told the built dif chunk i bought is out of an 86 GTU with 4 clutch plates vs the later model clutch difs that came with 3 plates (then the very late models with viscous difs). Will this fit in ANY TII dif housing?

The reason I ask is because I want the turbo ring gear because I've hear the NA ones shear teeth.
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