Torsen Differential - NA/NB Miata 3.63 Swap (Install How To)

Today we show you how to swap a 3.63 Torsen Differential into your NA or NB Miata. I'm finally working on the KMiata this week, and ditching the old 4.1 Torsen in order to prepare for the turbo install this coming winter. This swap is the mostly the same for all NA/NB Miatas, the only difference being the later NA8's and NB's all have a reinforcement bracket that is attached to the subframe and needs to be removed.
Music:
Clouds - Joakim Karud
• Clouds - Joakim Karud ...
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[@joelavallee3074]

I’m so impressed by how clean that car is! For a 91 it’s cleaner than my 2018 truck!

[@NappMotorsports]

The reality of doing a bolt by bolt “restomod” on it 2 years ago haha. Worth it now though.

[@malemerson1048]

Excellent video. It took me a couple of weeks to change my 4.1 to a 3.9. Broken bolts, a bad U joint and generally a rust ridden car. I would have used a 3.63 if I could have found one but the 3.9 is still an improvement.

[@NappMotorsports]

Right on

[@WigglingWaffles]

I've had a 6 speed/3.6 combo for almost a year compared to a 5 speed it feels like 1 - 2 - 3 - 3 1/2 - 4 - 5 worth noting is that 6 speed shifters feel clunkier and noisy until you find the right combination of fluid and shifter modification, then they feel incredible

[@NappMotorsports]

I’m debating on going with the Miata Roadster taller shifter for the swap.

[@jake10386]

Napp Motorsports have you had any reviews on the Gracing shifter? I was debating on that piece

[@r3vmixman]

I'm about to the same swap right now! Had to take a look at your vid for instructions.

[@NappMotorsports]

Hope it helped, thanks for watching.

[@MidnightMiata]

Very clean build! I've been mulling over getting a second Miata for N/A power, and this swap definitely seems like a contender. I definitely can't wait to see this turbo'd! Edit: Also, if you're at 3500rpm at 75mph you've got a 3.9 differential according to Flyin Miata's gearing calculator

[@NappMotorsports]

I could be off a bit. It’s definitely the 3.63. I’ve got different tire sizes and the gear in my trans might still be from the 1.6 with the 4.3 open diff. I’ll have to try it again. I noticed the other day when I was cruising that it was lower than I remember in the video, and 3300 rpm is 75 mph using the same calc on a 3.63. My gauges rattle a bunch because of the poly mounts, so I figured I was close with 7500.

[@MidnightMiata]

@@NappMotorsports I gotcha. Also depends on what tires you're running. I got a Torsen thinking it was a 3.63, but I currently run 225/45 tires at 75mph, and I'm at 3500rpm give or take. Still a massive improvement over the 4.3

[@aaronrunyon9959]

I like the tire rack, where did you get that?

[@NappMotorsports]

Amazon. It’s like $35.

[@Drthmnl]

@@MidnightMiata does going to a 4.3 lower the rpm or raise ? If im at 4k rpm on 5th gear going 80mph is that a lower gear ratio ?

[@kampfzwerg8135]

Thx for the video. Now I am much more confident to change my diff bushings by myself. Removal and Installation seem to be not that hard.

[@NappMotorsports]

Great!

[@ghostpunkkilla]

You put way more effort into cleaning that diff then I would have. lol

[@NappMotorsports]

You should see the rest of the underside of that car. I essentially restored it 2 years ago so it’s damn near perfect.

[@kennethdurapau1996]

Getting ready to swap in 3.63 gears in to my 04 MSM. To save a little money I'm bringing the shop just the diff.

[@NappMotorsports]

Definitely always an option.

[@handle690]

Fantastic camera work and guide. My only complaint is your voice sounds kind of monotone and bored with your presentation? I subbed man keep up the good work.

[@NappMotorsports]

Thanks for watching and the kind compliments.

[@positivesquad]

omg i have been looking for a video like this for ages. Thank you this is really helpful! Is is the exact same process for the nb? I am trying to torsen swap my 1.6 NB(yes there is a 1.6 version in europe)

[@NappMotorsports]

I believe it is nearly identical. There might be some support bracing that’s in your way but that’s easy to remove. Still weird to me that you guys got 1.6’s after 1993, especially in the NB.

[@positivesquad]

@@NappMotorsports 1.8 are much more expensive here(in good condition) I was able to get a really good 1.6 for really cheap. Most NBs here are 1.6. Thanks for the reply.

[@robertmetcalf3380]

I like the video and the way you presented the context. I have a nb and my rearend sounds like tires are out of balance but the tires are deadnuts. When I jack the car up, I grab the rear shafts and push them up and down with about an inch of play on each side. Is this normal or is it time to replace the bearings? It only does this between 65 and 72.

[@NappMotorsports]

I've never tested that myself, but that sounds like the traditional cowl shake that miatas get. I'd look into that before throwing money at it.

[@twistiepillowzjr.9751]

I am doing the same swap in my 1993 Miata I was wondering what year CV Axles you are using!? I'm stuck help please?

[@NappMotorsports]

Whichever ones match the new diff.

[@enriquealvarez4702]

Can you make a review on your control arm bushings. I'm undecided wether to go poly or rubber

[@NappMotorsports]

I’m actually in the process of swapping over to delrin in the rear. I’ll touch on it in that episode.

[@scottmason2245]

Wow....i thought mine was clean. Did you buy it like that or is that your ocd that got it that way? thanks for the video, im about to do a swap myself.

[@NappMotorsports]

Welcome to my OCD! I did a full restomod on the car 2 winters ago when I first bought it.

[@scottmason2245]

Wow though. Really really nice

[@robertdewerff1114]

Thank you, I needed this. 3.63 is my next step. Need to source some compatible axels. What tire size are you running?

[@NappMotorsports]

Wheels are 15x8 Entwistle RPF1’s (ET35??) Tires are 225/45/15 BFG Rival 1.5’s For axles, just go to rockauto and order new ones. They’re $55/side and come with the ABS ring gear, which works even in a non-abs car.

[@EnfieldJoe]

Great tech. Thanks for sharing.

[@NappMotorsports]

Glad you liked it!

[@dannysimpson9880]

Thank you for video I just picked up 1990 Miata 5 speed manual. not sure witch diff I have and if I need to change. making loud clunking from housing.

[@NappMotorsports]

It’s either an open or a VLSD. There’s some good user guides that will show you the visual differences. Swapping to a Torsen from a 94-97 is the best move though.

[@TheTamurai1]

You mentioned you kept the competition diff bushings, but never said what the red ones were. What company are the red bushings from called so I know to avoid it? I will also be swapping my diff and want to know the best one for the street. I Don't want anything harsh. I was considering going with the orange Supermiata 85 durometer bushings. What other bushings have you had experience with?

[@NappMotorsports]

The red one are Energy Suspension. I’d highly recommend the competition bushings for street use. My car rides super smooth on the street with little to no driveline NVH.

[@shirtz69r]

Was there any particular steps im reinstall? I note somr people have vibration issues if things sre not alihned properly.

[@NappMotorsports]

I’ve never had any issues. There are measurements you can take for alignment off the PPF

[@nclivin4220]

Are you aware if the entire subframe assembly from a 1999 miata will fit in an NA miata?

[@NappMotorsports]

This is an NB subframe actually.

[@gregorymahnken9682]

Are you using thinner on that tractor paint or just using it straight? I want to hit a few surface rust spots just starting on Amy's daily driver before fluid filming everything for winter. Sounds like I should use this instead of rattle can enamel?

[@NappMotorsports]

No thinner, just straight with the sauce. I don’t know if this is a rust encapsulation paint like POR15 though. You can get some of that rattle can converter, and then paint this over top and it’ll do the trick.

[@frederikpoppel9394]

I don't quite understand that... I have a 91 Miata with the 4.3 diff (I suppose) and it is going 3000rpm at exactly 100km/h (60mph) according to the speedometer. so if I swapped a 3.636 diff in there, I should get quite a bit lower rpm... though, you are exactly at what I am at with my stock diff. How?!

[@NappMotorsports]

I rechecked this yesterday when I was driving. At 3000 rpm, I’m at around 68 mph. With different wheel sizes, the new rear end, and the fact that my gauges have been modified, I think it’s reading a bit off. I had to use my laptop to show true RPM, and a gps to show true speed yesterday. Once I swap the 6 speed in I’ll worry about getting everything synced up.

[@frederikpoppel9394]

@@NappMotorsports hmm.. so maybe I need to check which differential I have. I mean, its not soo far off. Maybe I also have the 4.1 or 3.9 diff in mine. Need to check that. Though I really want mine to be a little more highway friendly as I want to reduce the emissions of my Miata. Not cool to use about 8L/100km while driving 60mph

[@philippe5249]

Your speedo/tach rpm ratio will not change, as the speed sensor is in the trans. But your actual speed (gps) is changing

[@rafe_3d160]

@@philippe5249 Is there a way to readjust the speedometer? I have been looking for this alot as I am doing some research on Miatas (I am a bored teenager, help me).

[@twistiepillowzjr.9751]

I have 1.6 shirt nose and the same diff you put it in the 3.6 is your drive shaft from a 1.8

[@NappMotorsports]

Yeah the driveshaft and axles have to match the diff, so if you’re doing a Torsen/Fuji/Open from a 1.8 you need 1.8 axles and driveshaft.

[@twistiepillowzjr.9751]

What year 1.8 Axles would I need? ​@@NappMotorsports

[@BokBarber]

Unbolted the driveshaft in my 90 NA for a clutch job, and the diff started leaking oil out of the pinion. I thought it was just the seal but when I went to size a socket on the pinion nut, it came off with finger pressure :(. I might be following these steps to get it out of the car, but differentials always scared me a bit. How difficult would you say a diff swap is compared to a clutch job?

[@NappMotorsports]

I’d say it’s significantly easier to drop the diff than to take out a clutch.

[@missmyvw]

I know you had a bit of a hook-up on tracking down the 3.63, but any insight in easily finding them given that they weren't ever available here in the states?

[@NappMotorsports]

Actually SNS Mazda Parts should have a bunch in stock. He just got a shipment in from Europe a couple months ago.

[@58Pittsburgh]

I got my last ppf bolt unscrewed and it’s sticking out a couple inches, I seen you hit it with a hammer. Do you mind explaining this to me, thanks!

[@NappMotorsports]

The ppf bolt on the front of the diff has a collar in it that you need to hammer out to get the PPF to unattach from the diff. Also sometimes on the way back in the sleeve of the bolt gets stuck and a couple light taps does the trick to get it the rest of the way in.

[@neverstopskateboarding8243]

I just got a torsen 4.1 and stub axles and axles that bolt up to it. I haven’t seen one person on KZbin with that set up. Did I buy the wrong thing? I see everyone else’s axles sliding in mine are a 2 piece

[@NappMotorsports]

No you’re ok! That’s a Type 2 I believe? The other Miata on our channel (Dylan’s) has that setup. It’ll work perfectly fine. Same exact process.

[@neverstopskateboarding8243]

@@NappMotorsports ya it’s a type two! I appreciate the help. I couldn’t even find help on the forums!

[@MANNA219]

What torque do u recommend for the 2 diff mount bolts that hold it to the subframe. Mines currently knocking because I think it’s not tight enough

[@NappMotorsports]

I usually torque them down to 4-5 Ugga Dugga’s with my big Milwaukee.

[@MANNA219]

@@NappMotorsports if you had used real spec I would’ve been lost. This was the comment I needed

[@scottmason2245]

Somebody help me!!!! Where can I get a torsen diff? Wanna sell the 4.1? I've been looking for a 2 couple weeks and I cant find one.

[@NappMotorsports]

Check out Alex Todd at SNS Mazda Parts. He can hook you up with a full diff swap. He’s on Facebook and Instagram.

[@scottmason2245]

@@NappMotorsports ty. I ended up getting a 4.1 torsen from treasure coast miata. Still have to put it in. Sure looking forward to it cause 250 with the stock 1990 diff just sucks.

[@LocoRocoNL]

Hi, 7:18, what are you using to clean up the mating surface?

[@NappMotorsports]

Without watching back, either a razor blade or a “cookie” wheel that doesn’t damage the surface.

[@lindkvistandreas]

rx7-diff cover ?

[@NappMotorsports]

This is a welded Miata housing.

[@ZareefHuq]

what RTV did you use?

[@NappMotorsports]

Permatex Ultra Black I think. Or Hondabond. Anything oil resistant should do the trick.

[@ZareefHuq]

@@NappMotorsports Thanks a lot! What brush did you use to clean your diff surfaces?

[@NappMotorsports]

Just some sort of metal bristle brush.

[@dankcincy]

ALWAYS REMOVE YOUR FILL PLUG FIRST!!!!

[@NappMotorsports]

Not a bad idea. I’ve never seen a stuck one though. For a transmission job I agree 100%.

[@ChuckNorris-ei2mk]

It's fuji not a torsen my friend

[@NappMotorsports]

Mine is a Torsen. You could get them overseas.

[@miatasta8521]

Löwundslö?

[@NappMotorsports]

I used to have a slammed MK3 Jetta with a VR6. Many years ago, but I kept one of the euro plates.

[@miatasta8521]

@@NappMotorsports that makes sense :D

[@beavishawk1]

Need jack stands.. Trust nothing

[@NappMotorsports]

The QuickJacks have a mechanical lock. They’re way safer and way more stable than any jackstands you’ll use.