Mazdaspeed Miata Differential differences

[iKhanh]

so i should be picking up a used differential from this guy who says it's from an '04 Mazdaspeed Miata MX-5. i've done some research, but can't seem to find out why it is, but from what i've read, the MSM is also a 4.10:1 ratio as it was used in some previous years. however, it is slightly larger and has larger axles too, which makes it exclusive to this model only. anyone know why that is? i'm just curious if it's in any way superior/inferior in terms of durability or performance than similar ones from other years. and can any of its components be substituted from another similar differential from other years?

any tips or advice when it comes to installation or servicing it? if you've picked up and swapped out a differential before, i'd like to know what you would do in my case. lets treat me as an oblivious fool. it's probably gonna have about 20k miles on it. i've never dealt with differentials before so i don't know what to expect.

[Hyper]

I want to learn if the differential bearing caps are compatible, look at my thread below. If yes, please confirm. Thanks!!!

http://mazdaroadster.net/showthread.php?2632-Differential-BILLET-CAPS-for-your-Torsen-KAAZ-and-OS-Giken

[RyanG]

The MSM differential case is more robust and the axles are larger and stronger. It does use the same 7" ring and pinion that all differentials used from 94-05. Only the slim chance that you do break and axle you will need to source another msm one because no other miata axles fit. The 4.1 gear ratio can feel a bit short but is actually a faster gearing until you are making around 300whp. If the car is more of a cruiser you may want to switch out the ring and pinion for a 3.9 or 3.6.

[Hyper]

The MSM differential case is more robust and the axles are larger and stronger. It does use the same 7" ring and pinion that all differentials used from 94-05. Only the slim chance that you do break and axle you will need to source another msm one because no other miata axles fit. The 4.1 gear ratio can feel a bit short but is actually a faster gearing until you are making around 300whp. If the car is more of a cruiser you may want to switch out the ring and pinion for a 3.9 or 3.6.


i am talking about the caps dude, the parts that hold the shafts, bearings, diff, and ring in place with the rest of the differential components. let me know or show me a picture to see the MSM parts without the pumpkin case

[iKhanh]

do i just open the case, snap a couple detailed shots of the bearing caps in question, and then close it? or is there a sealant that i should apply before closing it back up? i've never opened a differential before, much less touched one.

i'll get some detailed pictures when i have time. but it seems as if the axles are not stock, because from this http://www.miata.net/garage/diffguide/index.html, it doesn't have those tell tale signs of: "having four ears with a stud in each" and the pinion damper; however when i look at it from the side from where the axles slip in, it's a clear shot thru, as in there's no spider gear visible. the guy told me the axles were rebuilt (i'll ask him more about it after i get some more answers here and well before i even attempt to install), so that's a possible reason why they don't look like what the "stock" ones should look like.

[SM16RMSM]

The MSM uses the same ring size 7" as other Miatas but the actual case/differential is bigger and the axles are beefed up. I not sure on the numbers but I think the MSM uses 27mm axles and the standard axles are 21mm. Meaning, you can't use a standard Miata axle in a MSM and vice versa. I think the MSM differential is the same type of Torsen used as other Torsen Miatas, just that the MSM has upgraded axles. I think everything else is pretty much the same. If your not going to be pushing the 250HP mark, you really don't need the MSM rear end. A Torsen out of any other 1.8L Miata will work just as good and it also cheaper. On gearing, go with a 4.3 ratio if your staying N/A. If your going to have turbo, 4.1 gearing is nice with the 5 speed tranny. Sorry Ryan but your wrong, a 3.6 on a N/A 5 speed will just kill the performance, especially on a 1.6L motor. Here are the numbers and this is all based on a 7200 RPM redline and 205/50/15 tire size on the 5 speed transmission, top speed is 140 with the 4.3, 148 on the 4.1, 155 on the 3.9, and 167 on the 3.6. The only time you want to use the 3.6 or 3.9 is on the 6 speed transmission like in the MSM or if your pushing a lot of power down to the ground.

[Hyper]

i would like to see pics of both rear ends side to side

[iKhanh]

Both rear ends? So the MSM diff I got yesterday and my stock open diff? Carrier case open or closed?

[mini_fd]

I got a msm rear end on my car. This thread.is interesting and.im learning much from it. I have a 5 speed right now.and.plan.on getting a 6 speed to put in to make up for my gearing
its off atm

[Hyper]

the 6 speed sucks dude unless you are boosted. What are your plans with your ride??

[Hyper]

do i just open the case, snap a couple detailed shots of the bearing caps in question, and then close it? or is there a sealant that i should apply before closing it back up? i've never opened a differential before, much less touched one.
\\

Yes

and

Yes!, use silicon, clean and paint the pumpkin and let it cure until next day, put pictures of that thing here i want to see the MSM diff

[Hyper]

Both rear ends? So the MSM diff I got yesterday and my stock open diff? Carrier case open or closed?

Carrrier case open next to each other. I want to see the bearing caps for each and the size of the MSM diff compared to the 1.8 diff

[iKhanh]

i have a 1.6 open diff in my car. still wanna see that then? lol. any recommendations for silicon brand and where to get it? never had to use it yet so never bought some before. i work full time during the best time of day so i don't know when i'll get around to the install but i'll keep this in mind and keep you posted. i'll try to do it in a timely manner too; the sooner the better!

[iKhanh]

oh, and just an update for some folks here, which also brings up a new question. so while doing more research on the interwebs, i realized something: the tell tale sign of the "four tabs each with a stud in it" is only for the pre, mid-'95 Torsen's only where it still used two-piece half shafts. so since my diff was after that, it had one-piece half/stub shafts/axles/whatever, it doesn't have those tabs! apparently the previous owner had the axles rebuilt though, and they seemed to work fine before it was pulled from the car. on them now is just under 20k; is there any maintenance i should perform? i don't know if the diff itself has been rebuilt or anything though; i guess i could take a visual inspection of the gears when i open up the case. anyway.

new question: i read that the S2000 has the same differential unit as the MSM one. so if something ever does go wrong with my differential, is it possible to just swap out the ring and pinion set from a used S2000 diff and just swap it in? i'm sure the axles and driveshaft are different, so therein lies another possible problem. or has anyone ever done this before? i haven't looked on other forums yet, especially since i am only a member on here.

another question: as i've said before, i don't have that rubber pinion damper where the driveshaft meets the flange. is that bad, or is that a critical part that significantly changes the way it responds? is there a way to get a replacement? if so, where?

i took quite a bit of pictures yesterday. the pic dimensions are huge though so i'm gonna have to resize them before uploading them here. when i get home from work i'll do that, so hold tight, pictures will be on their way! except no pictures of the actual gears yet. those will come a lot later. ha

[ezmfne]

Look at solomiata I think they have some of the info you are looking for

[iKhanh]

I've been there. It doesn't really cover the MSM diff.

[SM16RMSM]

I got a msm rear end on my car. This thread.is interesting and.im learning much from it. I have a 5 speed right now.and.plan.on getting a 6 speed to put in to make up for my gearing
its off atm

In all honesty, you should drive mine and see if you like it, 6 speed not all that nice. Yes it will hold the power better but you'll need a 3.9 or 3.63 diff gear in offset the ratio. Put it this way, 5 speed vs 6 speed with a 4.1 rear gear, the five speed has a higher top speed. The gearing in the 6 speed is just too short.


new question: i read that the S2000 has the same differential unit as the MSM one. so if something ever does go wrong with my differential, is it possible to just swap out the ring and pinion set from a used S2000 diff and just swap it in? i'm sure the axles and driveshaft are different, so therein lies another possible problem. or has anyone ever done this before? i haven't looked on other forums yet, especially since i am only a member on here.

From my understanding, the look identical but I don't know if anyone has ever compared them to each other.

[Hyper]

oh, and just an update for some folks here, which also brings up a new question. so while doing more research on the interwebs, i realized something: the tell tale sign of the "four tabs each with a stud in it" is only for the pre, mid-'95 Torsen's only where it still used two-piece half shafts. so since my diff was after that, it had one-piece half/stub shafts/axles/whatever, it doesn't have those tabs! apparently the previous owner had the axles rebuilt though, and they seemed to work fine before it was pulled from the car. on them now is just under 20k; is there any maintenance i should perform? i don't know if the diff itself has been rebuilt or anything though; i guess i could take a visual inspection of the gears when i open up the case. anyway.

new question: i read that the S2000 has the same differential unit as the MSM one. so if something ever does go wrong with my differential, is it possible to just swap out the ring and pinion set from a used S2000 diff and just swap it in? i'm sure the axles and driveshaft are different, so therein lies another possible problem. or has anyone ever done this before? i haven't looked on other forums yet, especially since i am only a member on here.

another question: as i've said before, i don't have that rubber pinion damper where the driveshaft meets the flange. is that bad, or is that a critical part that significantly changes the way it responds? is there a way to get a replacement? if so, where?

i took quite a bit of pictures yesterday. the pic dimensions are huge though so i'm gonna have to resize them before uploading them here. when i get home from work i'll do that, so hold tight, pictures will be on their way! except no pictures of the actual gears yet. those will come a lot later. ha

please post pics and ask each individual questions for each thing. It is the best way to understand you dude

[mini_fd]

I drove a 10ae and.its.quick fast shifting and.goes threw the gears.to match the speed well

[iKhanh]

8367 driveshaft overall looks to be in good shape.
8368 so does the flange that mates up to the front of the differential.
8369 one of the axles. any idea what "6002 LH" stands for?
8370 here's the other axle. anyone know if it can be used on either side (left or right)?
8371 a rubber boot.
8372 a shot of the splines that go into the wheel hub.
8373 i see some grease oozing out of one of the boots; should i be concerned?
8374 a shot of the splines that go into the diff itself. the snap ring is noticeable here.
8375 just a different angle.
8376 once again.

[iKhanh]

8377 another boot, on the other end.
8378 a different angle. i don't know about axles, so what's with the huge splined piece?
8379 different angle.
8380 out of focus birds-eye view of the end that goes into the diff.
8381 and here's the pumpkin.
8382 some sort of stamp above the fill plug. does that tell me anything?
8383 i'm assuming i undo can undo all those bolts to open up the pumpkin exposing the ring and pinion, correct? and then when closing it back up, seal up the mating lips/flange with silicon? but there goes that stamp again.
8384 front of the diff, where the driveshaft connects to it.
8385 underside of one of the mounting arms. might be a good chance to change the bushings?!
8386 what's this little nipple looking thing on the back?

[iKhanh]

8387 you can tell it's a Torsen because there's no spider gear in the middle. clear as day on the other side.
8388 rear 3/4 view. where the axles slip in, you can see that perimeter seal looking kind of worn out. any idea on how to go about changing those, if possible? PPF bolt bushing things at the top noticeably loose from removal.
8389 yeah, that rubber seal is torn. or does it not matter? it kind of worries me. PPF bushings make a reappearance. also of important note is right behind the flange at the front of the diff for the driveshaft is the lack on a "pinion damper". any idea where to get a replacement? or is it even necessary? apparently automatic differentials don't have the pinion damper, but that also means it's not a Torsen (i think..? don't quote me on that). could i get away without having it?
8390 I forgot to add this to the first post of my pictures, but this end goes into the transmission, and looks to be in good shape too. it should just slip right on in despite it coming from a MSM 6spd if i'm not mistaken.

[Hyper]

the side bearing seal needs replacement is costs a few dollars,
do it or will leak!

from the pics posted the 1.8 housing that holds the pinion in place looks identical to all 1.8 diff except the rubber damper where the driveshaft connects. The rear pumpkin is way bigger I think is to increase the oil capacity but this doesnt say much about the internals. I wanted to see the MSM internals to see any differences. From the look outside the pumpkin has a bigger appearance that other years but again this is superficial, if any I want to see a pic of the pumpkin arms to see if they are beefier and stronger than other years.

FYI, the Rx7 pumpkin housing is way stronger than the 1.8 units

[mini_fd]

When i installed the msm rear end.i also installed.i think energy bushings. They are a red polyurethane mdiff mounts.

[SM16RMSM]

8378 a different angle. i don't know about axles, so what's with the huge splined piece?
8386 what's this little nipple looking thing on the back?

In the first picture, the ring your seeing is for the ABS brakes. The senors uses the ring to sense if one wheel locks up, and the other are spinning fine, the ABS module will kick in to relieve break pressure so you don't lock up the brakes. In the second picture, that nipple is a release valve. if too much pressure builds up in the diff, it is released through the little breather/valve so the pressure don't blow the seals out.

[iKhanh]

is there a specific name that seal is called? or if anyone has a part number? not sure if it's any different from other 1.8 Torsens. i'll get around to opening it up for you soon though. i work full time during the weekdays.

[iKhanh]

makes sense! thanks! i haven't had time to try installing it yet but do you think the ABS ring will interfere with any of the components on a 90 without ABS?

[SM16RMSM]

I'm pretty sure they are swap-able. I not sure if the housing are different. The rings are pressed onto the axle so you can take them off if you want to. Flat head screw driver and a hammer hammer helps.

[iKhanh]

from the pictures i've seen, the housing is different. but i just ordered in the seals. i think i'm gonna order in that pinion damper piece as well, just in case. i just wonder why automatic's don't have it.. won't be taking apart the case and take pictures until i'm ready to install the stuff.

[iKhanh]

8428 There's the Torsen in all its glory! With residual oil in the case spilling out when opening it.
8429 Side view. Notice the bearing caps, for Hyper.
8430 Bearing cap again, in good view.
8431 Birds eye view.
8432 The bearing cap on the other side.
8433
8434 The teeth look good.
8435 So do these.
8436 And this.

[iKhanh]

I got my replacement seals in the mail the other day. I read over the few threads that mentioned doing the seal, and the most helpful excerpt was this: "Pry out the old seal with a screwdriver. Be very careful not to scratch the seal bore. The seal is really in there so take your time. Once you have the old seal out, cut away all the soft parts so you can use it to install the new seal. Also, make sure you get the little round spring out. Sometimes, it stays behind in the differential. Clean the seal bore thoroughly with a rag. Lube up the new seal with lithium grease inside and out. To install it, press it in evenly with your fingers as far as you can. Keep it nice and straight. Then, using the old seal and a block of wood, tap the new seal all the way into the bore. The seal will go below the surface of the differential housing, that’s why you need the old seal. Make sure it’s completely seated and even when you’re done." -from http://www.miata.net/garage/diffseal.html

Anyway, I couldn't find any pictures so I figured I'll try to take some while I do this. The main thing I found was that I thought the seal was just just rigid rubber, but no, there's a flat metal ring that goes around it making it so rigid. If I had known this, I would have been more rough with the removal of the old seal. Note that I had done this while the differential was off the car, and also the case has been opened, making this SO MUCH easier.

So this is the replacement part you wanna get. I think they fit all Miata differentials (don't quote me on that), but I may be wrong. But this is the piece I ordered and it worked for me.
8437

This is what I'll be replacing, on both sides. The rubber has been torn on the outside. The other side looked similar, if not worse.
8438

And here it is on the other side, the side that you don't see, that goes into the differential carrier. That inner raised lip portion has a circular spring in it. Be careful of it falling out when prying on the seal, it's very easy to do so. I forgot to take a picture of said spring. Also, if you look closely, there's these slightly recessed squares in the seal; that's where a rigid metal ring is sandwiched in the seal itself. It's pretty stiff so don't worry about bending/breaking it when prying it out.
8439

You'll wanna try to pry it out like this if the differential is still in the car. Don't be scared to put some muscle into it.
8440

But since my differential is out of the car, I figured it would be easier to pop out the seal from the inside out, which was quick and easy. Just stick your flat head screwdriver in there, behind the metal ring in the seal, and tap on the end of the screwdriver like a chisel several times all around until the seal pops out.
8441

So where the seal goes into, the bore, have some solvent and clean it with a rag. Be careful you don't let any debris into the casing. I used some off the shelf generic Autozone brake cleaner and a shop towel. Mine turned out like this.
8442
And from the inside..
8443

Open up the new seal from the plastic it came in. Here's what a new one looks like. Notice that itty bitty round silver spring in the seal in that second picture. And in the third picture, you can see that metal ring in those squares I mentioned, without gear oil on them. Also, the seal came with that white ribbed gel already applied.
844484458446

Part 2 in the next post, since each post is limited to 10 pics.

[iKhanh]

Part 2 (cont.)

So apply some white lithium grease on the seal. Try not to drop the seal while you carefully position it for installation. Press it in as evenly and far as you can into the bore you cleaned a minute ago. Remember, metal spring side goes INTO the differential, and the cone shape faces outwards.
8447

Place the old seal on top of the new one, and with a hammer, pound lightly (but with enough force to progressively press the seal into the bore) around the old seal, to press in the new seal. You can get a block of wood and tap on that too I suppose.
8448

After you think the seal won't go in anymore, I suggest tapping with a little more force to make sure it is definitely seated in the bore. It should look like this after you're done.
8449

I think that's it. Any ideas, thoughts, comments, something, let me know.

[iKhanh]

By the way, these aren't the OEM MSM differential mount bushing things are they? They're rubber. They don't have the those raised circular sections, or is that the "competition" upgraded bushing? Should I go ahead and just buy aftermarket bushings? And what's better: Polyurethane ones or Delrin?
84508451

[mini_fd]

Poly is more comfortble and the in betweem of stock and delrin. Delrin is the most stiff out of the three

[iKhanh]

So I'll be attempting at swapping out my open diff for this during the holiday break. Any good ideas or advice I should know? I decided not to upgrade the differential bushings at this time; maybe in the future.

Since it would be kinda difficult to get gear oil into the carrier once it's installed, is the possibility of filling it up prior to lifting it into place in the car okay? And should I just lube up the end of the axle shaft that goes into the diff with the same fluid as lube?

[iKhanh]

bought some larger sized sockets (diff drain & fill plugs and axle lock nut) and i just wanted to share with you guys some of my findings: the 29mm socket fits the OEM axle lock nut on my 90 with an open diff, but apparently doesn't fit the old one that's on the '04 MSM; i'll be bringing it with me to the store and finding the appropriate size and update this when i can. AND while the fill plug on the original open diff on my car is a 23mm, on the MSM housing, it's a 24mm, which is the same as the drain plugs on both units.

update: according to this http://www.autopartswarehouse.com/search/?N=0&Nr=AND%28make%3AMazda%2Cyear%3A2005%2Cmodel%3AMiat a%2Cpart%3AAxle+Nut%2Cuniversal%3A0%29&PN=0&VN=4294961627+4294961536+4294967116+4294961618&domain=autopartswarehouse.com&query_type=Product+Results&Nr=AND%28make:Mazda,year:2005,model:Miata,part:Axl e+Nut,universal:0%29 website, the rear nut, is a 32mm size. i'll verify when i get a chance. probably won't be for a while though since i noticed that the cv boot ripped.

[iKhanh]

also, while perusing things, i found something interesting. all my previous research has pretty much concluded that the final drive ratio for the MSM is the 4.1:1... but on Miata Roadster http://miataroadster.com/mazda/mazda_ring_pinion_sets/g-63127.aspx, when you look at the Mazdaspeed model, it says it's a 3.636. now, Bill at Miata Roadster, great reputable guy, i'd value his expertise, so i'm a bit confused. is it a 4.1 or 3.636??

[MixedBreed]

I believe that list is for replacement gear sets that you can buy for that model, not the factory final drive ratio. So say you have an 04-05 Mazdaspeed, you can buy that 3.636 gear set from MiataRoadster to replace the factory 4.1 gear set in your car.

[iKhanh]

just thought i'd put this here. so in addition to axles that's unique to the MSM diff, the driveshaft is as well. seems that every other Miata driveshaft from 90-05 (non-MSM) has non-replaceable u-joints, but the MSM does! good to know.
http://www.mazda-speed.com/forum2/index.php?topic=27041.0