Alright.. so this has probably already been answered more than once but I didn't really look for very long. So the question is, does the N/A S4 LSD fit into the N/A S5? Any help on this will be much appreciated. Thanks.

Yes. As long as they're both n/a, it'll fit.

i believe that even a turbo diff should fit also but you need to change the shafts

I don't believe this is true. The turbo LSD is bigger, and won't fit in the pumpkin. You have to replace the differential housing with a turbo one. Also I believe the driveshaft and halfshafts have to be replaced. And if you replace the driveshaft then you also have to replace the transmission since the yoke won't fit. I think you can redrill the driveshaft though to make it bolt up...



*I think*



What I'm doing with my 89 n/a this weekend is putting a miata LSD in. It has to be from a 94+ miata. As far as I've read it's a direct swap.

I can't remember if I stated this before. But my 91 GXL has the TII swap done to it already with the S5 motor and tranny. I have the custom drive shaft from Mazdatrix for the TII to N/A rear end. So the only thing keeping me from buying it is if the S4 rear end is the same as the S5 rear end.

'86 to '88 LSD will fit into the '89 to '91. Depending on what you use the car for, you can actually view the S4 LSD as an upgrade since it's mechanical and not viscous.



Mechanical LSD will transfer torque better and provide better driver feedback (sometimes for the worse). A lot of drivers in drift, auto-x or time trials will take the mechanical version over the viscous just to get that feedback (and they're cheaper, lol).



A T2 LSD is bigger as stated before. You can swap in the entire pumpkin, halfshafts, driveshaft and tranny - but only the entire equation, not just part of it.



The redrilling of the flange works - but is HIGHLY not recommended due to safety. It leaves very little metal for the bolts to dig into and can easily break sending a driveshaft into the passenger compartment which at 6K RPM is going to be a bad day!

If you're putting an NA LSD into an NA rear end, you should be fine.

if you have a turbo engine and transmission why dont you put a turbo rear in the car?



why bother swapping NA diffs?

So in other words, you're saying that I can get a direct swap with the S4 LSD to change out my S5 N/A shaft since I already have the TII tranny and the Mazdatrix driveshaft makes up for the gap?

you still need the mazdatrix driveshaft as long as you stay with a NA rear end regardless if its s4 or s5.



if you go with a turbo rear you need the correct tii driveshaft, and of course halfshafts.

Because as One320B just said I'd have to have everything else i.e. the half shafts, driveshaft and pumpkin because the TII rear end is bigger.

Thank you. I think I'll go with this. Hahaha. All these other posts are beginning to confuse me.. because people are contradicting themselves. Thank you for your help.

I am not contradicting myself, neither was anyone else.



I am suggesting you save your money and efforts and apply them towards a TII rear end set up, you can usually get a whole rear end with halfshafts and driveshafts around $350.



if you want to stay with NA stuff your question was answered correctly by everyone except one person.

Well this one guy only wants 65 for an S4 LSD so I think I'm going to buy it. I would assume the TII rear end would be a little better for holding power.. but as of right now I'm kind of short on cash so I don't have 400 to spend on all that stuff.

why not just save your money until you can do it right, why bother if you are already running the car with a non lsd rear now.

Because then I'm also going to have to buy a new driveshaft. And from what I've heard not just from the forums but other people, the N/A rear ends are built pretty well, and they're able to handle a good amount of power. And right now, my car put down a little over 400rwhp and about 300rwtq.. so if the non lsd rear end can handle that I don't know how much more it would be able to handle, I think I might be pushing the rear ends limit, especially when I'm only running 14psi for when my motor is build for far more, and my MicroTech can go up to 2 bar.

400 hp and you cant afford a $350 TII rear end set up? For the $350 you can usually find a rear end AND driveshaft.





anyhow- as long as you dont launch the car from a stop too much it should last a little bit.

Then if you do blow it up what you have will be worthless at that point.

Now you could sell your custom driveshaft to offset some of the costs of a TII set up, if and when you do blow up the rear

end hopefully the driveshaft does not get damaged.

Haha. Yeah. All my money went into the motor, the car itself isn't all that great, the body is straight and so is the interior, but the exterior is just primer. The mechanic I paid for the job, kind of did a half ass job, so... he did everything to get it running. Don't get me wrong, he does good work, but all the money was spent on the parts to keep the motor together and to make the power.

still- what good is the power if you cant put it to the ground

Which is why I was trying to get a LSD to put it to the ground a little better.

Can I ask what you did to get 400rwhp? What model/year is your car that you dont have LSD... is it an SE?



I've blown NA difs up on less than 200whp, lol - it's all in how you drive it and what you use the car for. The FB guys are swapping axles and rear ends regularly at the tracks from hard shifts.



I will admit, it's odd you can afford a 400rwhp engine but not the extra $ for the rear.



I'm not bashing you, but it would be smart to put a T2 rear in with the driveshaft and halfshafts... you would feel a lot more confident in driving the car. It would worry me to death if I was cruising around w/ more than 300whp on an hand grenade NA rear end backing me up!

Hahaha. Sure.. I won't be able to name all the stuff I have, seeing as how I always forget some of it but here it goes



1991 Mazda RX-7 GXL with TII engine and tranny

Koyo Aftermarket Radiator

Precision PT71 GTS-H

2 Walbro 255's in tank

2 1000cc primary injectors

2 1680cc secondary injectors

NGK plugs

NGK Blue Wires

Front Mount Intercooler (Forget most of the specs but it's 3.5" thick)

Battery relocation kit (Driver side storage compartmetn)

Optima Redtop

Aftermarket Exhaust Manifold to move the turbo forward for clearance

3" downpipe to 2 2.5"

Mazda Speed 3mil cryo Apex and side seals

Huge street port (As big as I could go without bridge porting)

Pinned and Doweled motor

Stage 5 Comp Clutch

MicroTech LT10s

50mm Wastegate (Atmospheric dump)

Turbo XS RFL BOV (Which I absolutely hate and will trade for a Tial or sell)

Custom 2.5" intercooler piping

Polyethylene motor and tranny mounts

Mazdatrix TII to N/A rear driveshaft

Areomotive FPR

Block off plates

Coolant restriction to the top half of the motor

Oil Catch Can



I think that's about it.. I'll list anything else that I can think of that I forgot later. But yeah.. that's my little toy.. right now it's only on 14psi https://www.nopistons.com/forums/pub..._DIR#>/sad.gif One day I'll get it tuned again after I get a meth injection kit so that I can run more than 20ish pounds so that I can make better numbers! https://www.nopistons.com/forums/pub...#>/biggrin.gif

my bad when i posted i was talking about a stock turbo lsd and housing, but i see that you guys where actually just talking about the lsd alone... my bad, i always tend to refer the diff as one whole unit, lol

Coolant restriction to the top half of the motor?



Why do you need meth injection for 20psi? You've got 5360cc of fuel to use, lol... I think meth injection is a good idea, but if you've got a sufficient IC setup and the right fuel and timing, you should be fine to go at least to 16psi before you move into higher octanes, etc.



If you go to that 20psi level, you WILL NOT want the NA halfshafts https://www.nopistons.com/forums/pub...IR#>/smile.gif

Hahaha. I know. I need to get either the TII rear diff and assembly or aftermarket ones that can handle the power. Haha. And yes. I have all the coolant to the UIM and LIM as well at the TB blocked off. And thanks to the MicroTech I no longer have a BAC my idle is controlled by injector pulse widths. https://www.nopistons.com/forums/pub...#>/biggrin.gif

ALSO! I forgot to add this.. The meth kit.. will allow me to be able to run a little more lean with the fuel in the higher boost range so that I can get more power out of lower boost. It's just something that I've wanted to do. *Shrug*

I see about the coolant now, when you said that, I thought blocked the water jackets in the "top half" of your engine, lol..



As for meth, I understand the purpose - i have to use it on the REW FC project since i'm running 24psi. My IC is efficient, but over that 16psi level, meth is just added insurance.

Exactly. That's why I wanted the meth kit. I don't really feel like blowing up 10,000 dollars. Hahaha.