Own a 91 na coupe RX7. Has an open diff & that needs to change. I've tried searching for this but cannot find exactly what I'm looking for. Would like to install an LSD into the car but I'm not sure what all LSD's swap into this rear. Here are two links. Will these work or no? What should I be looking for also?

http://www.ebay.com/itm/Jdm-fits-RX7-FC-FC3S-Viscous-OEM-LSD-Rear-Differential-Slip-Kit-Side-Flange-/371115279621?pt=Motors_Car_Truck_Parts_Accessories&fits=Model%3ARX-7&hash=item566831c505&vxp=mtrhttp://www.ebay.com/itm/Mazda-RX-7-RX7-non-Turbo-NA-FC-13B-LSD-4-10-Differential-Ring-and-Pinion-Gear-/360780804947?pt=Motors_Car_Truck_Parts_Accessories&fits=Model%3ARX-7&hash=item5400363353&vxp=mtr

 

The answer is right in the FAQ on the top of the page
also, they are all swappable

 

Yes. But less work if you stick to an NA LSD.

 

No. All JDM cars were turbo. Turbos had a bigger ring gear than n/a so it won't work.

Unless your current car is, or started life as an auto it already has a 4.10 rear so no need for the ring and pinon. I read the torsen unit out of a Miata works. Supposed to drop right in to the n/a pumpkin. You will have to use your ring gear on it though.

 

Open NA diff to NA LSD was stupid easy to swap. there is no messing around, everything bolts up the way its supposed to. Honestly i felt that removing my dashboard was harder than dropping the rear end out and doing the swap..

 

Thanks for the info guys. When I had my car on my hoist it looked pretty straightforward. And should I be looking for an S4 na lsd or an S5?
And for confirmation it is a 5-speed

 

S4 would be preferable as it is the clutch type, though it will probably need rebuilt as by now the clutches are probably worn out.

 

I would suggest an S4 NA LSD since they are clutch type instead of viscus.

 

I would put a 1.8L miata torsen LSD in it... it'll be much better than a 25 year old S4 clutch type.

you definitely don't want an S5 viscous LSD.

 

Like so?
http://www.ebay.com/itm/Miata-94-up-T-2-Torsen-LSD-NA6C-NA8C-FC3S-non-turbo-RX-7-Kia-Sportage-4x4-/361179316794?pt=Motors_Car_Truck_Parts_Accessories&hash=item5417f7023a&vxp=mtr

 

yes

 

whats the difference in the miata vs s5 diff? I thought they were both torsens?

just out of curiosity and for the sake of posting info that might be useful to those who search for it

 

The S5 is a viscous diff, not a torsen.

FDs have torsens too

Viscous Coupling - HowStuffWorks