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....Z-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