90 Miata Transmission Upgrade(s)/Rebuild
 

Hey everyone, picked up a $40 5 Speed with the shift knob sawed off at the turret ball. I've rebuilt transmissions from a variety of makes and models.

I must say the internals are some of the most frustrating with the many C-Clips and Roll pins. Not to mention the large nuts and long shafts..

Anyhow the transmission in the car is doing all right. Got some noise on overrun, that quieted up after the change to Torco MTF. It has not gotten worse, but will need replaced in the future.

I have reviewed the parts diagrams on Jim Ellis Honda, and have saved copies of the gear shafts and forks for the years 91, 93, 94, 97, 99; and for the most part they look the same, apart from the turret changing. Also, I have reviewed the parts list at AdvancedAutosport from Dave as well as a few other threads and sites.

I have also come across the TSB regarding fixing the 2nd Gear, sleeve, hub, and synchro on these older units, as well as an updated unit in the 94+. These hub/sleeve/synchro are different part numbers despite everything else connected to it having the same part number, including the shafts and shift forks. Why is the TSB for the 90-93 call for a different assembly than 94+? Can I use the 94+ in the 90? Differences? This is what makes me confused.

Along with this there also is a TSB for the shift change lever, A>B>C without a clear explanation for what changed. This adds to list of potential parts to pick up from Mazda, unfortunately not from MazdaSpeed, maybe I will have to go to a few AutoX to sign up, if the transmission lasts.

It seems that in addition to the standard Bearing, Synchro, and Seals, I plan to upgrade this as far as possible while it is open. I have heard talk of shift forks being updated by Mazda several times, but lack the recent part number, or adequate description. Is it on the interlock side or the hub side?

In addition, I plan to replace the reverse sensor, the 5-R rod, all the C-clips, roll pins, springs, copper washers, nuts, other damaged parts during rebuild.

I was hoping the collective minds on here could help me devise a list of current parts that can be used to upgrade even the oldest transmissions to the best condition.

Thank you

A 6spd out of a 99-05 would be a great upgrade.

I understand the benefits of upgrading to a superior model, however I do not have the money for a new 6-speed transmission, but look to restore what I have to like-new at a reduced cost.

I also enjoy the challenge and learning process with each new transmission I repair. Gain tools and knowledge. Perhaps down the road I will pick up a used 6-speed to rebuild, but have heard from various sources they are notably more difficult, and starting off with the simpler variant.

I have read a copy of the enthusiast manual explaining the procedure to tear down and rebuild, I also have replacement bearings and seals. I plan on deburring all the gear engagement teeth and sliders when its apart, as well as a few other tricks..

Thanks

I paid $300 for my used 6-speed. Had ~60k km on it. Shifts like a greased unicorn, no rebuild necessary.

While the price I paid is atypical of current prices, there are good deals around. Just keep a look out.

Welcome to miataturbo :party:

Bump for serious discussion. I tried to lighten it up to make the read less dull. I figure many of the avid enthusiasts have worked their way to the turbo world and then this site.

I am more that willing to post links to resources I've been looking at studying this application. From many forums such as Grassroots Motorsports, Spec Miata etc, but could not create multiple threads on all of them.

It seems like you guys break them rather often, and fail to see they will eventually run out as predecessors have. I find enjoyment in restoring and upgrading cars rather than the quick gratification achieved from scrapping and swapping in another used unit. If anyone can help point me to a more technical forum or knowledgeable user, that'd be great. It seems there is always a Tranny guru or two in each community. I'm hoping to replace any known problematic pieces, such as the 2nd gear assembly, but lack complete understanding of the revisions.

Thanks again

I honestly don't think i've ever even heard of anyone trying to do this. Once someone breaks enough 5 speeds, they jump to a 6spd or a Quaife.

I'm very surprised nobody has made dog box gears for a miata trans.

99.9% sure they're out there. Open your wallet. And your anus.

a quick google search says in the 14k range. That is also surprising. as i can find a t56 dog box gears for 10k.

C'mon lets stay on on topic, I am not interested in a Dog box, 6 speed, quaife, used swap box.

Are you guys telling me that the Subie, Honda, Chevy and others have better build/repair capabilities? You are generally a minority, but you have MazdaSpeed..

Just looking for some people knowledgeable about the 5 speed boxes and their revisions.

It appears according to the exploded views that the updated 2nd gear assembly and synchro is interchangeable. They ride on the same shafts, and use the same shift forks and rods.

I actually believe you could even take a new turret off, and slide it onto the old transmission, and have it work with the remodeled tailshaft/shift lever assembly..

I just wanted to reiterate, I got this working 5 speed for $40. And you all are using them as consumables. But I bet you if I shoved this transmission away for 10 years under a tarp, I'm gonna have no problem ridding it for $400, even if I didn't monkey with it. What other investments do this. I have a collection of STD crankshafts from desireable cars worth stupid money, all bought for under $100 apiece. I've watched it happen over and over with different model cars.

I like the manual transmission! And I think you all do too. It is a great possibility they will stop being produced by common auto manufactures in the futures. Something to think about.

Turns out, my girlfriend drives the miata, and I bought this as a learning exercise for her. It can go back together the way it came, rebuilt, but seeing as I've done this a few times, including a few straight cut boxes, and like to challenge myself so I don't become old and negligent. Her car is a B package 91, stock as hell. Modified NGK wires, Plugs, 94.5 Type 1 Torsen LSD, 1.8 Driveshaft, $110 Carquest Axles (Fingers Crossed), MazdaComp Engine Mounts, ES RSB Bushings, ES Diff bushings, CNC Skou/DIY reroute. Fixed the stock audio with a Kenwood Deck, Polk 3.5(4) 6.5(2) Speakers, Blaupunkt 50x4 RMS amp and rewire it all 14G as per Jeff Anderson. We got the hard top and a new glass soft top. 15x8-9 6UL 225 RS3v2. The car is fun.

I'll let this thread cook a little longer, see what it comes up with. If nothing, Ill come back

I keep forgetting you can't delete posts entirely on this site.

No need to delete anything,

1994 - 1997 Changes:
Added a Shift Rod Interlock Pin (R501 17 351)
Upgraded 3rd-4th Shift Rod (M504 17 421A)
Upgraded 2nd gear Synchro (R504 17 26Y)

2nd Gear

I was not however able to locate the first 2 updates on a parts diagram, and suspect they may be incorrect or out dated. Im about to contact Mazdaspeed request information, but wonder if they will provide support not being a member.

The 2nd gear synchro seems to go on the same PN hub and sleeve, and are reflected in the attached gear pics.

I currently have the "C" revision and wonder the difference with a "Y" seems to defy the revision patterns. Curious if it's worth getting the other.

Part Number Description Quantity Interchangeability
New Old
M502 17 265C M502 17 265B 2nd Synchronizer Ring 1 New -> Old
M503 17 262A M503 17 262 1-2 Clutch Hub Sleeve 1 New -> Old
M505 17 260B M505 17 260A 1-2 Clutch Hub Set 1 New -> Old

Source: http://www.miata.net/garage/tsb/s004_92.html

Notice it calls for the C synch,

Also, even in the 94 diagram with the Y synch, it still calls for the old hub.
Confirming my suspicion that the diagrams are inaccurate. Can anyone share the MazdaSpeed ones?

Change Lever - >
M524 17 510C Change Lever

^Change Notes?

Source: http://www.miata.net/garage/tsb/sb005_93.html

5-R Fix
M506-17-431A reverse rod
M506-17-640A Switch


Source: http://www.miata.net/garage/stuckreverse.html

3-4 Shift Rod/Others
Maybe I will be able to find the shift mechanism change in 3-4 as well.

Thanks

Credits/Motivation:
Miata Transmission Changes 1990-2005 - MX-5 Miata Forum
Jimellis Honda

The reason you can't find any information here about the 5-speed is because we break them in ways that cannot be fixed. There's minimal interest in tweaks to shift forks or synchros when all the teeth come off every single gear at ~250wtq.

Miata owners are cheap as fuck. I bet 99% of the people on this site would ever consider spending 10k on gears, let alone 14k. Especially when it becomes more economical to v8 swap when you get above 6 speed breaking power levels.

I do not believe that they will always break, especially after a refurbishment with new bearings holding the gears securely in place.

Wear is loose, and loose gears have play, or lash. As that lash doubles the force of it slamming x4. I bet almost all of you have 5 speeds with wear and very few have used a rebuilt one based off the attitude on here.

The conditions at which a 5 speed breaks is largely variable on transmission starting conditions, driving style, and engine configuration, etc. Saying something is rated for a specific HP or TQ is asinine in my experience, and hardly every concrete. That being said, I don't plan to ever venture above 250wtq, and enjoy the 5 speeds.


You're right, most people on here do not have thousands for a tranny, possibly because they wasted it all being foolish.

Learn to polish a turd rather than scoff at the idea and you might be worth something more than what is in your pocket. Do the turbo guys just buy their way through the journey, rather than learning like the N/A guys?

I dont see more than $400 going into this thing, or why this contribution/venture is any less significant than others. Post count? You guys post count club? This could help a lot of people out. I know you guys love talking about dicks and shit but thats about only universal thing I've found on this site. Embracing the gay-aura I suppose. Cool for you guys.

Ok, so I might not be able to find information here, which is disappointing. Can anyone recommend alternative sources, forum or people?

For informational purposes, our 5-speeds contain many of the same internal parts as the 5-speeds in the 1st generation RX-7. Perhaps that will be of use to you.

I have a friend who races spec miata. His mechanic rebuilds 5 speeds for him, refreshing almost everything in them. I have seen those rebuilt 5 speeds break within a season of use multiple times. You may not believe that the 5 speed's are week, but after 10 years playing with miata's I have seen a ton break, and not ever seen anything that would fix them from breaking again. So go ahead and spend a ton of time and money refreshing the 5 speed. Maybe it won't break on you, maybe it will, but overall we collectively have enough experience to know it is a waste of time and energy.

To reinforce what's been said already, here's what a 5-speed gearbox typically looks like once we're done with it:

https://www.miataturbo.net/attachmen...ine=1437165138

That ain't gonna be fixed. Which is why we consider transmissions to be in about the same category as brake pads once you get to a certain power level- it's a disposable wear item.



Several years ago, Flyin' Miata worked with Quaife to put together an upgraded set of gears for the 5-speed box. The raw gearset sold for $2,700 and they offered an assembled transmission for $4,000 on an exchange basis (+ $450 core charge).

Miata owners being the chronic cheapskates that we are, everyone whined that it was too expensive, and FM quietly discontinued the product a few years later due to low sales volume and claims that it "did not live up to expectations."


Also note that while the 6-speed gearboxes are a tad stronger, they are, rather annoyingly, geared even shorted in 6th than a 5 speed is in 5th. This means that RPMs will be higher at a given speed after installing a 6-speed gearbox unless you also swap out the diff (or R&P gears) for a taller set. (The 6-speed cars came with 3.909 rear gears, as opposed to 4.30 or 4.11 in the 5 speed cars. To really take advantage of a 6 speed in a high-torque car, you need to expend some shoe leather and track down one of the unicorn 3.636 sets.)

3.636s aren't unicorns, they're readily available from Mazdaspeed. They're just expensive ($550 plus another $100 for the VSS plus $250 for setup because you probably don't have the tools to DIY it).

3.3s are unicorns, as in rumored to exist but nobody has ever seen one.

--Ian

Moti from blackbird has a post somewhere (locust maybe) where he finds the rumored 3.3 r&p and it doesn't fit. Pretty sure it's fully a unicorn.

Fair enough- I meant in terms of the junkyard market.

I managed to snag one out of an 80s-vintage 626 for around $100, but it took some searching.

Calling something a Spix's Macaw (critically endangered, yet not entirely extinct in the wild) doesn't convey quite the same meaning. :rolleyes:

It's as if none of you comprehend shit.

Perhaps why so many of you are incapable and poor, not to mention break shit so often.

Your tags are great, shows high maturity level and skill present here.

I dont give a crap about how poor the average Miata enthusiast is, and I never said shit about a Quaife gear set. You are still out there arguing with your dumbass-self about shit I don't care. It may be a waste of time and money for you, but thats your free, worthless opinion that does nothing for this thread as far as productivity. The majority of the posts here other than mine are absolutely 100% bullshit and just shows how dumb you 1000 post users really are.

I figured it out by contacting more useful sources. Transmissions are nothing like brake pads, only perhaps the synchro and cone. That failure of the gears doesn't spontaneously happen in a perfectly rebuild transmission with a driver using the correct driving style, despite what your confident uneducated mind(s) seems to think about it. I have worked in various fields and witnessed almost every type of failure. Stripped gear teeth are the product of shock loading and excessive play in the shafts due to worn bearings. I am confident this gear set can hold at least 300ftlbs given the proper conditions.

Thanks for nothing Miataturbo.net

Your confidence is misplaced, young padawan.

Shitty thing about people like this is we know he won't come back when he blows his 5 speed up. So we never get the satisfaction of being right :(

:bowrofl:

:bowrofl:

:bowrofl:

:bowrofl:

:bowrofl:

:eggplant:

Being ignorant and in denial must be so frustrating.

The tags in this thread are actually pretty tame by comparison.

I can't remember which thread it is, but in one of the more popular ones, I'm actually accused of being a brony.

I have no idea why...

Attachment 233139




It's not spontaneous, in that they typically don't explode just sitting there on the bench or when the car is parked. Usually it doesn't happen until you put the car into gear, depress the throttle, and release the clutch. Sometimes it takes multiple applications, depending upon the amount of torque being produced by the engine, the engagement rate of the clutch, and the stickiness of the tires.



Well, understand that this being MiataTurbo, shaft play is something that we tend to enjoy.

That having been said, I wish you the best of luck. In all seriousness, you will impress a lot of people here if you manage to wring any serious amount of use out of a 5-speed transmission at >300 HP, presupposing that you drive the car in a reasonably spirited manner.

Nothing like a good laugh at work.

"Hi. I have next to zero experience with high power Miatas, but I'm going to assume that I know its transmission's limits better than people who've spent years, if not decades, racing them, and sometimes, running businesses based on more-than-doubling their stock power outputs. When presented with information from these people, I'm going to call complete strangers poverty-stricken idiots, because at 21 years old, I'm that much better than everyone."

Regarding transmission availability: if 5 speeds were in danger of becoming extinct, you wouldn't be able to pick them up as easily as you can for a couple of hundred dollars (or, apparently, $40). The fact of the matter is that the subset of the hundreds of thousands of Miata owners out there who will actually make enough power (or run them hard enough on the track) to break transmissions is miniscule, and Miata chassis are being lost to attrition far faster than transmissions are grenading. If this weren't so, the laws of supply and demand insist that the prices would go up, and it wouldn't be this easy and cheap to find transmissions for a car that's been around for longer than OP has been alive.

Although OP will refuse to admit it, transmissions are breaking because they can't handle high torque. Experts theorize that it's the transmission case itself that flexes, causing misalignment of shafts and the subsequent total destruction. At stock power, in anything but full-on racecar abuse, they usually live for hundreds of thousands of miles.

Internet Anonymity.

Are you twelve?

This is the same asshat who jumped down aidans throat for offering a perfectly acceptable solution to his problem.

https://www.miataturbo.net/wtb-7/wtb...1-8-lsd-85248/

BAN BAN BAN BAN BAN BAN BAN BAN BAN BAN!!!!!!!!!!!!!!!!!!!!!!!!!

It's entertaining watching someone be so bitter, ignorant, and in denial.

Hahahahahahah wtffffffffffffffff!

This dude sucks.

And the whole time I'm thinking:
Oh and LAWL @ miata parts skyrocketing in value. Good luck in 200 years, you're gonna ball so hard.

Thanks for the sig, BTW

OP you know people might have taken you more seriously if you proof read half the shit you wrote. you might be a tranny whisperer but i cant under stand shit you said in the first page.

also we miata owners are not poor idiot we just know where tho put our money were it wont come back and bite us in the ass.

I think you should take you attitude back to HondaTech

lol