blew a tranny this weekend
 

the second session in the morning of a three day event. awesome.

so what is the typical fail point. I was in third gear, heard a high pitched sound and then no gear. im going to send the oil in to black stone to see if heat caused a break down.

any advise? not sure I want to go 6 speed,

You probably want to go 6-speed.

If you want to stop breaking transmissions as often, you want to go with a 6 speed.

well how often are people who track hard breaking their trans? I got the car, did 2 pretty easy sessions and 2 pretty hard sessions and it is toast.

I guess their is know way to really say.


do we we know the root cause of the failure? was someone taken it apart and looked at what is failing it? if it is just too much power fine, but seems like it could be heat related, the shifter under the ---- boot was very wet with fluid, perhaps it was overheated or perhaps the previous owner over filled it?

There is supposed to be fluid there in the 5-speed, people break 5-speeds ALL THE TIME, and the failure mode is just too much torque. You're not that new here, how do you not know these things?

From what I've read, people who track turbo Miatas with 5 speeds see that transmission as a consumable.

The bottom of the shifter is supposed to be wet with fluid on a 5 speed.

It really is if you track a miata then the 5 speed is a consumable. Having a turbo does not change that.

A couple of buddies and I tend to agree that the 5spd due to the PPF will twist and and stretch the case resulting in blown gears. Looking at the ribbing on the 6spd.

I watched another member here (cordus) blow 3rd (iirc) out of his 5 speed on the front straight of MRLS about a month ago. He's running a similar setup (FMII, 2560, 3" exhaust) so yes... at your level on the track, its not unheard of.

FWIW, I believe he's going 6 speed.

I'm about to throw up.

You most likely did what the rest of us did, which is sheering teeth off the gears. Same thing happens in 1.6 rear ends, at least mine did. I'm sure if an oil cooler made a 5spd reliable we'd all run $300 cooler systems over $700 transmissions, but that's not the case. And as much as I'd love to be proven wrong, cooler oil doesn't keep teeth from snapping off.

fair enough, but Ive only been here a few months and Ive spent a ton of time reading about every trouble spot on a track turbo miata and personally I think Ive done a good job getting this car track ready. do you track? I do about 15 or days a year minimum usually more, a lot more. Ive worked on my car almost every night for several months so cut me some slack. I know the 5 speed trans failure is common but Ive not ran into posts about specifically what is failing so just want to find the most cost affective way to make the trans reliable.

Im going to open the box and see what happened. just wanted some basic info and no one said anything about the different versions of the trans and perhaps changing out 3 for a stronger gear.


someone said I needed real brake pads. I had zero brake problems with willwood E fronts and HPS rears. it is shocking to me as well but Autobahn is not that hard on brakes so I'll see what is needed when I do blackhawk in a couple weeks. fyi the alcon temp strips on the caliper did not even darken one block

The most cost affective way to make the trans reliable is to spend the $600-$1000 for a 6 speed.

well with my limited experience on gear failure fluid temps can have a major affect. In FSAE we had lots off diff problems due to oil, we had lots of diff failures in a diff that was designed for a very heavy car. when the teeth mesh well all is fine but with added heat in time the gears wear and they dont mesh right then they fail so anything that can be done to slow that wear will extend their life significantly. once the wear starts it is all over.

I'm sure much of this has been tried but I asked about trans temps and I did not see a good answer. please dont throw up, just trying to learn from people who really ring out their cars at the track. if the 6 speed is the answer then fine I will do it but I just want to know the details before spend the money on a box with 6 gears when I only need the 5.

I almost blew out my colon this morning.

I think they have other forums for that.

You broke the 5. You need the 6. This is much, much easier than you are trying to make it. The failure mode is broken gear teeth, usually in 2nd under power or 3rd after a hard shift. The 5-speeds break at 200whp with abuse, or at 250whp without abuse. Fluid temps probably make it worse, but there are autocross cars that break 5-speeds too. There's a guy in Washington (bbundy) who broke SEVEN of them before finally giving up and switching to a 6-speed.

The 6-speed is bombproof at 300whp, and it starts to become a consumable (once every 12-18months) at 350+whp. At your power level (FMII) it will last pretty much forever.

ok got it, it was not a hard shift but a nice easy rev match down to 3 and, back on the gas on a kinda double apex and when I squeezed the throttle on track out I got a weird wine and a pop clink clink, almost like a linkage came apart. took it apart and no linkage in this trans, shifter goes right into the trans.

I have way too much work to do on this car to ---- around. I still want to think temp and good fluid management could be the answer but it sounds like other have been down this road despite not not seeing any temp numbers. whatever if it will last Ill do it, think I found a 50k unit for 700 not to far from home. guess I should get it and not look back.

I have several events coming up, every weekend in june and I need to get this thing reliable this year. a friend and his f-in cup car need to be put down now ;) he he ....> (thinks a turbo miata can not be reliable on the track.,,,,, going to prove the sob wrong ;))

on to suspension, cant buy coils, thinking spec miata even though I know its not great at least it work for the season and I can sell it easily

I just talked to dave at red line and he was very helpful in general terms about the mt-90 trans fluid recommended for our trans.

a recommended fluid temp is about 190-195f - at that temp the viscosity is 19.5
for comparison 300f it is 6.5 at 330f it is 5.3. - the temp people have seen on the trans housing via temp sticker

so we know a temp over 300f is well into the range a cooler is needed. a viscosity drop in a engine like this would be scary. this is is why many run a fluid that has a high viscosity when hot. Ive been running motul 300x 15-50 for this reason, my motor gets hot! keeping the temps down to around 200f would make sure the fluid is doing its job and not turning into water.

this is not to say a trans failure is not going to happen but it does suggest that heat is the real enemy of the trans, and not necessarily the power. I think our trans would do much better with a cooler but buy how much I dont know.

fabricating a oil cooler for the trans is not hard, nor is it easy and the cost might be a wash when compared to doing the 6 speed. I;m on a time crunch so I may just do the 6 speed but I do think this deserves more exploration. If Ive missed the boat speak up but without track testing I dont care. I want to see a new 5 speed run at about 200F and see how long it lasts.

This is an interesting theory and makes some sense. If the case flexes the right way, it would move the shafts apart which reduces the contact area of the teeth (making them easier to shear off). High horsepower Honda's use a handcuff to reduce shaft separation but it converts the gearbox to a 4 speed (not recommending that as a solution, just showing a similar problem exists in other applications).

I understand the 6 speed is the easy way to go but I also like the idea of fixing a problem. ;) Please post some pictures of your trans when you pull it apart.

I work at a shop that builds high performance, upgraded trannies (DSM, Evo, 3S, Supra, the occasional RX-7). The number one killer of gearsets is torque, and the only way around it is higher strength parts. Tolerances, preloads, specific detailing, etc can be adjusted to make sure a trans shifts as well as possible which can help a bit. There are a few ways to upgrade a DSM trans, for instance, with higher strength gears/shafts so that they are good to about 600whp, but that's it. Beyond that, nothing else has been shown to help. There is a limitation to any material that is subject to high stress for extended periods of time, and the 5 speed Miata gearbox apparently was just not designed to take much abuse.

That being said, I'd guess in a roadrace situation higher trans temps can and will play a part in the deterioration of the oil, which will lead to greater wear on contact surfaces, and the extended time heatsoaked could probably lead the gears to fatigue and fail sooner. The only time we've modified a manual trans for an external cooler was on the Chumpcar we ran a couple years ago, and that was due to the fact that it was going to be run in an enduro, not just 30 minute sessions. It was not a simple procedure, requiring the addition of a mechanical pump inside the trans, case modification and welding, etc...pretty much no room to do that with a Miata trans as far as I can tell.

from my previous post, the temps are way too high, but Im sure torque plays a roll well. road racers are not launching and my trans was in gear, for at least a second or 2 out of a corner before it popped so it was not a issue power engagement it was a mechanical failure due to heat, and over time the fluid breakdown and added power caused failure. i'm not an expert but Ive seen several diffs and trans fail in this way on power and I think the heat has a lot to do with it.


red line said it does not really break down till around 400f but they clearly state the viscosity between 200f and 300f is about 1/4, so its like a 3x lighter weight oil at 300 versus 200f.

@ 195 viscosity is 19.5 ( est recommended high temp)
@ 300 viscosity is 6.5 ( this is well into the range you should have a trans cooler)
@ 330 viscosity is 5.5

the 300 temp was based on husler temp sticker, which I presume is a brake temp sticker which simply darkens as each temp benchmark is met. his temp and our temps may be higher


I would really like to see some info on someone who tried a external cooler on a 5 speed and decided it did not work. a setup on a trans that was known to be in good shape.

I was throwing up at your sentence, not your idea.


And like I said please try it. It won't be a waste of money, just time. If it doesn't work it'll bolt up with a little modification to the 6spd you eventually buy. A well placed cooler, an electric pump, a well place return and feed line, and voila. Tell us how it goes and how much it costs. Like I said, I'd love to be proven wrong.

In gear for a second or two so its not torque?

How about the increased torque in gear after a second or two as the revs rise and the boost builds?

In the weakest gear in the box, which is allowed the most flex due to being in the middle of an unsupported shaft in a gear where you are getting 100% traction.

Thats got nothing to do with why is failed in 3rd after a second or 2 in the gear?

Dann

Granted, most of the transmissions we build go into cars that are launched more than road-raced, but that does not stop 3rd gear from being the most damaged individual gear we see. Even from a roll or a smooth upshift, the teeth on 3rd will shear off given enough power.

I'm definitely interested in seeing results from this, and your plan for pumping the oil as well. Not trying to discourage you, just tossing in my .02 from seeing lots of trans damage. If you come up with something that can save a bunch of money for a lot of guys, in the long run it'll totally be worth the effort.

I'm simply saying that I think heat is causing damage to the gear faces which eventually causes failure. if the torque was the issue, it would rip the teeth off almost as soon as you put on a turbo. I'm pretty sure the gear is getting worn out prematurely due to the due to a lack of sufficient lube caused by excessive heat. one the gear faces get worn the lack of a tight fit causes the gears to smack together and fail. this is a fair hypothesis. I'm sure the torque is a factor but I don't think the torque is killing the trans.

my first step is to send the fluid to get checked out and we shall see what they say. I think I can get a pump for nothing so would just need to figure how to lay out some fittings. my the end of the week I will have the trans pulled and I will take some pics.

has anyone done a cooler ?

I think cars that get launched for drag may have a different set of issues versus a road race car. that said, if you say 3rd is is most often failed gear then I would perhaps agree my heat argument may not be correct.

Yeah, I shattered 3rd gear at Laguna, coming out of turn 11. FM hardware, built engine, making 270 at the wheels. It had been whining in 3rd gear for a while, so I knew it was on its way out.

Here's the last few seconds of life in my 5-speed. As you can see, I was in 3rd for the corner, then when I put the throttle down for the straight it went bang. The tire screech is from the red car in front of me :)


The car has an MSM 6-speed in it now, with a 3.9. I've got a 3.6 R&P sitting on the bench waiting to go on the diff that just came out.

Note that it's $600-1000 for the 6-speed, but you really need to swap the rear end as well. The 4.3 would be useless, the 3.9 is annoying with a turbo, the 3.6 ought to be a lot better.

The other option is the Quaife gearset for the 5-speed, but the gears alone are $2500+ and I've heard (anecdotally) that the increased strength isn't enough and they still break.

--Ian

1. Amsoil > Redline. Redline fluids run screaming into the corner at the first hint of high temps - the Amsoil MTG that I use now doesn't seem to be phased by it. I've done some UOAs of both and the Amsoil is a far, far superior fluid.

2. They break in AUTOCROSS. A cooler will help on track, sure, but not in an autocross situation.

My 5speed is still holding on. However I make no torque so that could be the reason. I'm honestly baffled because I drive the car hard, and have missed a few gears before and crunched it multiple times on the track. Yet it still functions. I won't go 6spd until this one blows.

if I need a 3.6 R&P, what car does this come out of and where can I find out. I think I recall reading they are expensive and hard to come by. so what will the effect be if I leave the rear end the way it is? I doubt the 6th gear is shorter then the 5 in the 5 speed. if so that sucks big time.

The 3.6R&P comes from a mid 80's 626. If you search on mt.net you can find threads with the exact info in them. Realistically you will not be finding a used one in the junkyard. You can buy them new from a few vendors on mt.net. They run around $550 or so new.

The 6th gear is shorter than the 5th in the 5speed. The 3.636s can occasionally be found in junkyards for cheap, or you can buy them brand new from Mazda for $500+.

Hey Phil, if you tear the trans down post some pics of the remaining teeth on your broken gear, or of the other gears which survived, or both. Some good overall shots, and some macro shots that show both sides of the teeth, so that the surfaces are clearly viewable. That will go quite a ways towards figuring out what happened.

I would have guessed the 3.9's were a good match for the 6speed. I have 4:10's in my 6speed and everything seems quite happy.

I wonder if I can get it from mazda speed discount program for racers, anyone checked this out?

Yeah was going to do it today but I had to work. I will have it out by the end of the week for sure. I was going to go pick up a six speed this week but now I'm not sure I want to deal with taking apart the diff just to achieve the same gear ratio. if anything I would like a slightly taller gear. its possible the po may have done a shorter final drive for drifting.

I'll get some pics for sure, speak up if they are not good enough. perhaps I'll have you build be me one good for 1000 whp!

It is $500 from Mazdacomp (that's where I got mine from, part # MA02-27-110). IIRC it's more like $700 from other vendors, but I don't recall who they are. Note that if you want your speedometer to be correct you'll also need the correct VSS, which is another $100 from Mazdacomp (M528-17-400A is the part #, I believe).

The 3.3 is the gearset that many people want with the 6-speed, but it's unobtanium and may even be mythical.

--Ian

The 3.3 is the gear set that many people want with the 6-speed, but it's unobtanium and may even be mythical.


so what should my 99 be in the rear? according to this article my final drive should be 3.3 but the axle ratio is 3.9, what number should I be looking at. my car has a 5 speed but I believe it was replaced with a 95 trans due to a failure. so it sounds like the 6 speed is stock for a 99? I'm still new and learning the year to year changes so bare with me.

http://www.motortrend.com/roadtests/...a/viewall.html

The Motor Trend article has a typo in the spec list (they get it right in the text).

Your 99 is a 4.3 unless it's a 10th anniversary edition (10AE), in which case it's a 3.9. The MT article is about the 10AE. The 10AE is the only 99 that came with a 6-speed.

NA 1.6s came with 4.3.
NA 1.8s came with 4.1.
NBs with 5-speeds came with 4.3
NBs with 6-speeds came with 3.9 or 4.1 (varies by year)

This is all in the USA and for manual transmissions. Other countries and automatics may be different.

http://solomiata.com/RingandPinion.html

--Ian

I'm going to go pick up a 6 speed because I still have a lot to do on the car and I dont have time to dick around. I strongly considering mounting a spare temp probe in the drain plug just too see what the temps are inside. I have a some vdo gauges from an old project I can use.


should I open the case to inspect the gears before I install?

the leak I was experiencing was coming from the trans, not the engine so I think i'm going to leave the rear main alone for now and just put the new trans in. or should I really order rear main and trans seals?

what do you guys think about adding a heavy oil to the trans. like 75-110 or 75-110? most people run 75-90 right?

https://www.miataturbo.net/album.php...pictureid=2406

what do we need to post a picture, Ive tried the baisics but i'm doing it wrong

Hmmm....so the PPF may be a cause?

The "BB code" link. Copy and paste it:
https://www.miataturbo.net/picture.p...pictureid=2406

https://www.miataturbo.net/picture.p...pictureid=2407


noticed this on my nice new trans, thinking of splitting the case just to see what is going on inside.

Stop spreading bullsh*t. The older M.NET threads speak about 2 failures over the last 5 years in non-Miata applications.
Yes, they are not cheap to get, they not cheap to get in your trans but have not broken under power in a Miata application.

No, read up on the old M.NET thread. During the Quaife gearset development they checked for case flex and was found to be a non-issue.

anyone have pictures of the bare gears? they look sleeved. has anyone attempted to do a rebuild at home?

Beyond the obvious, you'll probably need a press and gear/pulley remover. I have not seen any pics of a disassembled Miata trans or individual gears, but here's a link to manuals with exploded views: http://www.mazdaspeeddevelopment.com...miatapubs.html Otherwise take a bunch of pics of specific bits if orientation is not obvious. For example, in DSM trannys some parts fit in the clusters both directions and seem to be correct, but only work properly one way.

yeah lots of pictures for sure, but for some reason I never get the pictures I need.

I think the disassemble will be a learning exercise more then anything. several gears have chips so I don't think it will be economical to repair.

I'm going to stop by a place that makes gears for industrial applications perhaps the can make me some super strong gears might be cost prohibitive but it does not hurt to ask

so I was expecting the worst but this 6 speed seems super clean and seems to shift great. The inner shift boot was toast so I replaced it and the linkage bushing from the 5 speed and bolted it up. I also ordered a ebay shift knob for the miata, because my old momo king knob always loosens up.

anyway so far I dont see what all the fuss is about. shifts just fine, but as others have said, it can be hit or miss. for once looks like I caught a break.

Yeah, mine shifts fine as well. It's not exactly like the 5-speed, but it's a lot better than I expected.

6-speeds shift fine. Anyone who thinks they are crappy should go drive any BMW.

6-speeds with good gear oil in them shift fine. With shitty oil they can be a pita.

FYI for those that dig up this post, I hated the 5 speed when I got the car, it did not feel right, I took off the light weight shift knob and put on an old heavy momo king knob at a slightly higher position. I could not believe how much a difference this made. about 1/2 inch higher knob and a heavy knob vs a light one changed everything for me and I loved how the car shifts. so just something to consider if you don't like how the car shifts. just get something heavy and and slightly taller and all is well. also someone on ebay sells a shift knob spacer that might help if you run a supper low, light knob with a short shift kit.

the oil that came out of my 5 speed looked like muddy ---- water. the fluid that came out of the 6 speed looked new. I hope the previous owner did a rebuild and promptly crashed his car.

I know exactly what you mean. The oil that came out of my 5-speed looked like a chocolate milkshake :barf:

yeah not sure if that means the oil breaks down due to heat and then is filled with metal or if it is just filled with contamination and little pieces of metal. I know they make heavy gear oil like 74/140, it would be interesting to run this see what happens. I did not feel like screwing around, trying to trouble shoot but I will post the results of the blackstone oil test when i get them back in a couple weeks.

In your new to you 6-speed the consensus is to run Amsoil. If you need a hook-up on it shoot me a pm and I can get you in contact with someone who sells it.

to get the car running I used redline that came with the car so I can make sure everything works, I'm going to order engine oil and trans and diff oil soon and I would like to get the amsoil and the motul oil from the same place if possible. lll pm you. thanks

the car shifted fine with the engine off. I drove the car and it was really bad in to 5, 6 and R. I changed out the shift knob, for the big heavy momo king i have and tried it again. It shifted fine into all gears. the slightly higher position and the heavy knob made a big difference. point is, if you have trouble with a 6 speed, get a heavy knob and figure out a way to make it sit a bit higher. I was starting to freak a little but it just goes to show, little changes can make a big difference.

AND... I just blew my 5 speed too :vash:

Any tips on where to find a 6 speed quick? I've got a race next weekend.