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codrus
codrus GRM+ Memberand HalfDork
9/18/13 12:09 p.m.

The MSM 6-speed is generally considered the strongest bolt-up transmission for an NA/NB Miata, so they're in high demand among the turbo weenies who have destroyed multiple 5-speeds. They are especially valuable when offered for sale in the paddock at Laguna Seca during the annual Miatas @ MRLS event... :)

Swank Force One
Swank Force One MegaDork
9/18/13 12:11 p.m.

^To that effect, if you'd like to keep the stronger transmission just in case you want to make power more than a 5spd will handle down the road, swapping to a 3.9 or 3.63 rear end makes the 6spd much more liveable as well.

Personally, i'd LOVE a 3.9 rear end in mine right about now. I don't feel like i'm making enough power to properly use a 3.63.

Keith Tanner
Keith Tanner GRM+ Memberand MegaDork
9/18/13 12:26 p.m.

Yes, that's definitely the time to have one for sale :) A street-driven MSM with a LE shouldn't tickle the 5-speed one little bit.

Xceler8x
Xceler8x GRM+ Memberand UltraDork
9/18/13 12:30 p.m.

If you're swapping the 6 spd for a 5 spd you can also use that time to upgrade to a Flyin Miata happy meal clutch kit. They have clutches to hold whatever you need. My stock 1.6 clutch started to slip at 7-8lbs of boost. I installed the suggested kit and never had clutch slip again.

Keith Tanner
Keith Tanner GRM+ Memberand MegaDork
9/18/13 12:37 p.m.

Actually, the MSM unit is pretty good, quite a bit better than any of the other stockers. As much as I'd love everyone to buy an FM clutch, it's not needed in this particular case.

wvumtnbkr
wvumtnbkr GRM+ Memberand HalfDork
9/18/13 12:48 p.m.

Is the 3.9 rearend teh same as teh one out of a 2nd gen non-turbo RX7 automatic? If so, I would probably be willing to trade the one I have for a 4.1 out of a miata.

Also, is the 6 speed really a bolt in / out affair? Do the tail shafts interchange between the two? If so, I would like to put the 6 speed in my rx7!

Rob R.

MadScientistMatt
MadScientistMatt UltraDork
9/18/13 1:58 p.m.
bigmackloud wrote: Hmm, so it boils down to the gearing and the ECU. The rest can be fixed relatively simply. That's a shame, seems like a deal breaker.

And expect a new, relatively easy fix for the latter very soon.

Swank Force One
Swank Force One MegaDork
9/18/13 2:01 p.m.
wvumtnbkr wrote: Is the 3.9 rearend teh same as teh one out of a 2nd gen non-turbo RX7 automatic? If so, I would probably be willing to trade the one I have for a 4.1 out of a miata. Also, is the 6 speed really a bolt in / out affair? Do the tail shafts interchange between the two? If so, I would like to put the 6 speed in my rx7! Rob R.

Wouldn't engine-side bolt pattern be different?

Keith Tanner
Keith Tanner GRM+ Memberand MegaDork
9/18/13 2:04 p.m.

The 6-speed really is a bolt-in/out affair in a Miata. All external mounting points are the same. Not sure how it will interchange with RX7 parts.

The MSM has larger halfshalfs with a different spline count than other Miatas. It's actually the same as an S2000 rear, IIRC. So the normal Miata interchange rules are changed a bit.

wvumtnbkr
wvumtnbkr GRM+ Memberand HalfDork
9/18/13 3:15 p.m.

I bet it is the same rearend as teh Turbo II rearend then.

The 5 speed NA miata trans is exactly the same as a RX7 trans except the tailshaft length and bell housing bolt pattern. The gear ratios might be slightly different as well.

I realize that sounds like a lot, but I recently took a miata trans and shoved teh spin-y bits inside my FC case in order to have a working trans. The bearings, shifter, everything is the same. The tailshafts are interchangeable to get teh length you want. They are also interchangeable with an FB rx7 or a mazda B2000 pick up.

I am wondering if the 6 speed is similar to lego together.

I bet this is a similar trans to the RX8. The rearend is probably the same as well now that I am thinking about it.

Rob R.

codrus
codrus GRM+ Memberand HalfDork
9/18/13 4:54 p.m.
wvumtnbkr wrote: I am wondering if the 6 speed is similar to lego together.

My understanding is that the 6-speed is an Aisin unit and is totally different internally from the 5-speed. Supposedly it shares some internal bits with the one in the S2000, but I don't know any further details.

I have an MSM 6-speed and 3.636:1 gears in my car, it works nicely. 1, 2, and 3 are almost identical to 1, 2, and 3 in a 5-speed with 4.3:1 car (which is what my car came with stock), 4th and 5th are a tiny bit lower, and there's an extra freeway gear. I ran it with the 3.9:1 ratio briefly and hated it.

The 6-speed has a unique shifter (actually I seem to recall that there are 2 or 3 different ones for different years of 6-speeds), and I think there might be a starter bolt that doesn't fit. The neutral and reverse sensors had different connectors from my 5-speed, so I needed to cut/splice those, and when changing the rear end you also have to swap the VSS to get the speedo to work. It bolts right up to the PPF & engine, you keep the same clutch, same slave cylinder, same driveshaft, etc.

Keith Tanner
Keith Tanner GRM+ Memberand MegaDork
9/18/13 5:20 p.m.

The starter bolt moved in 1999. NB 5-speeds have the same starter bolt pattern, but nobody noticed until the 5-speed showed up. There are a couple of ways to make it work, including just leaving the bolt off.

Driven5
Driven5 Reader
9/18/13 8:33 p.m.

Codrus has the right idea! If I still had my MSM I would have swapped the rear gear for the 3.636, and would never have even considered pointlessly swapping the transmission. The 5-speed offers no real advantages over this, since in my humble opinion the 5-speed does not even shift appreciably better than the MSM 6-speed. As noted, the 6-speed with 3.636 offers essentially the same exact gearing as a normal Miata with 5-speed, but then has an extra gear on top of it for highway cruising.

codrus
codrus GRM+ Memberand HalfDork
9/18/13 9:54 p.m.
Driven5 wrote: The 5-speed offers no real advantages over this, since in my humble opinion the 5-speed does not even shift appreciably better than the MSM 6-speed.

I'd have to say that all of the 5-speeds you've driven have been broken then. My MSM 6-speed is supposed to be one of the best-shifting 6-speeds around, and it's nowhere close to as good as the 5-speed I took out. Well, technically after I took it out it was only a 4-speed, with a big hole after 2nd, and lots of little crunchy bits inside it... :)

Keith Tanner
Keith Tanner GRM+ Memberand MegaDork
9/18/13 10:00 p.m.

An excellent 6-speed will shift as well as an average 5-speed in my experience. Add into the fact that you'll pay $400-600 for a 3.6 and you could make almost that much with a 5-speed swap, and it might seem less pointless.

Every single person at FM preferred our Mazdaspeed after we put the 5-speed in, mostly due to the shift quality. The number of missed gears dropped dramatically.

Driven5
Driven5 Reader
9/19/13 12:38 a.m.

Sure the 5-speed may shift a little more smoothly, but that doesn't mean the 6-speed is a bad shifting transmission by any means either. In my personal experience and opinion, the MSM 'shift quality' thing has typically been blown out of proportion. Although, maybe I'm just not sensitive enough to shift quality. Yet adding the 3.636 gears to the 6-speed, would help improve what was my #1 complaint with both the MSM and 1.6L NA I had owned...Which for me personally would have been more critical to my long term enjoyment of the cars than the few hundred dollars to be had swapping away the MSM transmission. At that point, you might as well just buy a car that already comes with a 5-speed in it and from what I have seen can generally be purchased in a faster state of already-turbocharged tune for less money than an MSM (or MSM+LE) anyways.

Swank Force One
Swank Force One MegaDork
9/19/13 9:04 a.m.

I fixed the missed shifts in my MSM 6spd by installing Mazdacomp engine mounts, poly diff mounts, and rebuilding the shifter using a MiataRoadster delrin shift bushing.

Honestly wish i had gone harder on the motor and diff mounts. Thinking about going to the AWR 70A engine mounts and a set of delrin diff mounts. May just try the Beatrush rear triangle brace first.

Some Amsoil MTG helped the shifting as well. Once warmed up, my transmission shifts like butter. Still doesn't like to go in reverse from time to time, which seems to be a common issue in MSMs in particular.

Keith Tanner
Keith Tanner GRM+ Memberand MegaDork
9/19/13 9:46 a.m.
Driven5 wrote: Sure the 5-speed may shift a little more smoothly, but that doesn't mean the 6-speed is a bad shifting transmission by any means either. In my personal experience and opinion, the MSM 'shift quality' thing has typically been blown out of proportion. Although, maybe I'm just not sensitive enough to shift quality. Yet adding the 3.636 gears to the 6-speed, would help improve what was my #1 complaint with both the MSM and 1.6L NA I had owned...Which for me personally would have been more critical to my long term enjoyment of the cars than the few hundred dollars to be had swapping away the MSM transmission. At that point, you might as well just buy a car that already comes with a 5-speed in it and from what I have seen can generally be purchased in a faster state of already-turbocharged tune for less money than an MSM (or MSM+LE) anyways.

The MSM and the 1.6 NA are the Miatas with the shortest gearing The 1.8 with a 5-speed and a 4.10 is one of my favorite gearing combos, especially with a moderate amount of boost behind it. Others prefer the 3.9 with the 5-speed.

Swank Force One
Swank Force One MegaDork
9/19/13 9:58 a.m.

I find the 6spd/4.10 combo less irritating when driving the car hard. Yeah, you're shifting a lot, but you're generating a serious amount of thrust not normally associated with the relatively mediocre power my car makes.

Or you can treat it like a big block and just roll 3rd and 4th gear in really tight sections and let the car drag you out in 3rd instead of dealing with the manic inhalation of 2nd gear that happens in about a half second out of a 30mph corner.

Really the only time the 6spd/4.10 combo really bugs me is driving around town or on the highway. Unfortunately, that's 98% of where the car is driven.

codrus
codrus GRM+ Memberand HalfDork
9/19/13 11:09 a.m.
Swank Force One wrote: Really the only time the 6spd/4.10 combo really bugs me is driving around town or on the highway. Unfortunately, that's 98% of where the car is driven.

I found that the 6-speed/3.9 left me shifting up to 3rd and back down to 2nd 3-4 times on our typical local autox course, while switching to the 3.636 reduced that to at most one time. 270hp at the wheels has something to do with that, of course. :)

Swank Force One
Swank Force One MegaDork
9/19/13 11:11 a.m.

Yeah, i think i'm only around 240whp, hard to tell with the gigantic variations between the two dynos i've had this car on. (50whp+ spread, lower number is faster.)

kanaric
kanaric HalfDork
2/25/14 9:44 a.m.

Bumping an old thread but I have some MSM questions:

Is finding a a 3.636 R&P set a good solution for the gearing issue? Or is the trans still too terrible?

How do you deal with this overheating problem? Intercooler upgrade or something more?

Is there any easymode ecu solutions like nistune or megasquirt pnp for this car or would I have to build my own?

edit:Looks like I found an answer to my last question: http://www.bellengineering.net/product_info.php?cPath=4_37&products_id=722

just thought about it, doing something like that to a OBD2 car makes a car fail smog tests doesn't it.

turboswede
turboswede GRM+ Memberand UltimaDork
2/25/14 9:51 a.m.

In reply to kanaric:

A piggy back is probably your best bet to deal with emissions compliance.

turboswede
turboswede GRM+ Memberand UltimaDork
2/25/14 9:54 a.m.

Some of these items might help in and around the stock ECU:

http://flyinmiata.com/index.php?dept=68

They do have an ECU solution, but it isn't ODB2 compliant. Hopefully someone here will come up with a solution for that.

kanaric
kanaric HalfDork
2/25/14 10:23 a.m.

Can a piggyback take care of the issues with a MSM? I know for some cars with ECU issues sometimes the piggyback can only do so much.

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