If case flex is the root cause of 5mt blow ups, how is a tougher/harder gearset going to survive either? Maybee I'm wrong, but it seems that even a gimme/KAAZ/or whatever will shave and blow if misaligned by flex - right? Does anybody know for sure? Suby techs? Hello? SOA has got to know something about all these tranny's they are swapping.

Seems a 6mt is the only money well spent, if case flex is the problem.

it's a combination of problems, not just case flex.

case flex is the major problem
the input shaft being very long is another problem
first second and third gear not being large enough is another
problem.
all gears have an improper heat treatment from factory, they're
fairly fragile.

case flex can be dealt with, it doesn't really do a whole lot of
harm as long as the rest of the gearbox is designed properly.
the problem is the combination of all three. the long input shaft
causes the case to flex under high load. as the case flexes it
pulls the first gears away from the driven shaft.

instead of the load being distributed completly across each
tooth of a gear: as the input shaft pulls away, the gear slides
away from the gears on the driven shaft. as it moves away, less
surface area on the teeth are able to cope with the load. already
weak gears struggle to cope with the load, and the teeth
strip off the gears.

So you see, it's not just one problem, it's a combination of several
problems that lead to the distruction of the stock gearsets.
hardened gearsets can withstand more, typically the teeth on
first and second gear are wider as in the RA gearset, so even
if the input shaft was to pull away, the gear could still hold the
power.

in the Kaaz gearset, the first few gears are straight cut instead of
helix (is that right?) cut. the stock gears engage each other by
sliding together, each tooth as it engages can only handle so
much load at once, they're suceptable to stripping eaisly; especially
if they were not treated properly during manufacturing.

straight cut gears don't engage by sliding together a piece of the
tooth at a time. they preety much slam together and form an
instant joint, so by the time they're ready to take the load from
the engine, there is complete contact going on between the face
of the teeth. This is what makes them stronger, and also louder.

scuzzy, well put. Really well put. Someone has done thier homework.:) I freaked when I ran across this topic. There were no answers except it's the driver. Don't buy it, so I went looking. I will add some info if you do not mind. Some is not asked for but will help some someone.

Yep, KAAZ, BMP, PAR, MRT and most others except Gimmies use spur cut 1-3 or some variant of that. 1 and 3 and five, or 1-2 only etc.... In fact you can even get dog 1-2 and synchro 2-5. All manner of forms and ratios, engagements and cuts can be had. They all have stronger shafts and in some cases bigger ones as well.

Straight curt gears are louder. Straight cut gears do not generate end thrust, which otherwise places irregular loads on the gearbox bearings and the main thrust plate. Entire face of tooth contacts entire other face of tooth. Much bigger contact patch. Much louder. Usually better material. More material, lower tooth count, Easier to make. Much much much stronger. OEM can do it. Too loud though. This is key. MUCH stronger. Serious about drags, these in dog is perhaps your nirvana. Dog engagement on the street is not so good. Lightening shifts as there is no waiting for synchros. Generally, dog engagement is not intended for daily city driving and will wear quickly under those condisions. Dog 1-2 may be viable as most shifting is 2-3-4-3-2-3-4 and so on. At least for me.

Helical gears turn inot one another. Helical cut siphons some power in that not all of the force transmitted goes to turning the gears. Some of the force goes to pushing the gears sideways against the thrust bearings, resulting in lost power. Much smaller contact patch. Much quieter. Much weaker. More difficult to cut. Can be made much much better and stronger with more material, better material and more optimized tooth count though. Just not by OEM. Too expensive to do industrial grade. Big win done right. Drag enough with 400wtq, break these too probably.

The looooong input chaft of questionable strength deflects under torque as there is no bearing as it inters the case. Some weird seal. That is it. That shaft deflection is what causes case flex. Flex is really a symptom of a weak shaft. The engine is not twisting the case. The force causing the flex/twist is coming from inside the GB. The cause of the flex is the input shaft. Flex is a sympotm.

As scuzzy covered, the combo of weak components, gears, shaft, case and material lend them self to failure. Especially under load. Sometimes. Why do some guys run 300whp and wtq and never have a problem? This is what fuels the "tase great, less filling" part other wise known as "the driver, the manufacturer". Well quality control problems is a strong possibility. I guess some come from here some come from there. Probably out sourced to vendors. Get them from the good vendor have no problems. This is a plausable explanation not necessarily thre correct one. No one knows for sure, unless you want to blame the driver in every case. That's cool too.

What is a boy to do? Stronger case would solve it. So would a bearing at the front of the shaft. Own a machine shop. I am there!Then again, so would a thicker stronger shaft of better grade material. Pretend I am Groucho with a cigar here, "that is what my wife says" Have you seen that MRT shaft? I do not know if any of these have been addressed in the 6MT. Perhaps all, perhaps none, prhaps some. I am guessing I will find out in the next reply.;) 6MT may be the silver bullet. Don't know.

Common question is how loud? Ever driven in reverse? Straight cut gear. Well that gear is short so not that loud but you get the point. Faster you go louder it gets. Ever watched racing footage in car and heard a whinning and said that engine sounds funny. It's the gears. 4-5 helical make it livable.

Dragging can break anything. Some like MRT warrant them if does break and will replace them even in competition use. If you are not dragging and are autocrossing then a new better quality gearset should fit the bill. With the RA set, well the jury is still out on that one. I have heard of people hearing of failure. You know how that is.:rolleyes:

Ultimatly, collect all the info you can, analyze it and come to your OWN conclusion. Or listen to someone else. That works too for some. If you do, please do not defend it like you know what you are talking about. That is what causes confusion on this topic. My hypothesis may be wrong but at least I arrived at it using information and tools available. I am always willing to change my opinioin if there is some new fact exposed. I am betting $4500 includng labor that I am right. $10,000 on a 6MT? Buys you an extra gear. Hey, that may be worth it!

Gimmies for me probably. They have more material than the 6MT per gear too I believe. No drags for me. Just my $.02. Take it or leave it. May be wrong, may be right. At lease I can sleep at night! Good luck with what you choose to do.:cool:

Great followup post :)

I prefer to use the Kaaz Gearset, even if my car is on the
street most of the time. Usually because I don't play easy
in my vehicles, I dog them out. Squeel tires, burn clutches.

All in the name of spirited driving. I'd rather have a little extra
wear on a Kaaz gearset than have complete gearset failure
on the stock set.

It all boils down to how loud can you stand it? the Kaaz gearset
has 4th and 5th Helical cut, so they're quiet. but 1-3rd are
straight cut, and they'll be LOUD. Is it worth it for me? Yes. I'm
building a performance car, not a showcar. I don't know of a
single gearset they make today that can handle over 500HP
and also be as quiet as a helical.


you can get a Kaaz gearset from Rallispec for about $3300,
that includes the install kit and everything needed to finish the
assembly. minus tools of course. It's synchromesh, so even though
1st through 3rd are straight cut, you won't play hell trying to shift
them :)

But you can get the Kaaz or Gimmie synchro gears and have the car be perfectly streetable (besides the increased noise, of course) right? If I save up money, I'm gonna be getting one of the two synchro sets, because I'm not patient enough to learn how to drive on dogs ;)

Originally posted by gjhsu
But you can get the Kaaz or Gimmie synchro gears and have the car be perfectly streetable (besides the increased noise, of course) right? If I save up money, I'm gonna be getting one of the two synchro sets, because I'm not patient enough to learn how to drive on dogs ;)

Hehe, that's what I'm doing. the Kaaz gearset.

BTW, if even that fails, there's always the dog box. Hell a dog
box tranny is the strongest type of transmission in the world.
diesel's put out over 2000ft/lb torque and all they can use is
dogbox transmissions...


given their tranmission weighs 3/4th a ton and the clutch weighs
200lbs alone.. that's still a hell of alot of torque :D

Oh yeah, you should always rev match on down shift with synchro. Upshift smoothly not harshly as well. Do not bang the gears in like they do on the strip. Dog engagement however, actually work better shifted faster. If done slowly they drag, make noise and wear. There is no such thing as too fast for dog. Dogs love the fast shift with authority. No matching needed as there are no synchros. That is what you are waiting on.

Lightened flywheel should help. If not, you have to wait for the hardware. As long as you are spending that amount, look at the MRT. Seriously.

The KAZZ have the lowest 4 the and definitly 5th on commonly available form. Your car will always feel like it wants to attack the road by the way. If everything is strong enough, and the sudden shock is great enough and the wheels can not get going fast enough, given enough torque and shock load you could theoretically burst the case. It would have to be soooome load though. :banana:

Thanks a ton, you guys.

I used to build semi-custom trannies for Triumphs when I was in college, so what you say makes perfect sense to me. One of the trannies I had was non-synchro first gear . I actually really liked it. The power transfer effieciency was definitely noticiable. Talk about having to rev-match, tho. You had to be dead stopped to go into 1ST. It had no sychro or dog engagement of any kind.

Just so people know, when straight cut gears are not under load, they are quiet. You could get a straight cut 1-2 and helical 3-4-5 and be very happy.

Where are people looking at MRT gearsets these days? Kaaz is Rallispec, and gimme is direct, right? Maybe gimme should do a GB and ten of us will hunt up secondhand trannies to rebuild.

Originally posted by scuzzy
it's a combination of problems, not just case flex.

case flex is the major problem
the input shaft being very long is another problem
first second and third gear not being large enough is another
problem.
all gears have an improper heat treatment from factory, they're
fairly fragile.

case flex can be dealt with, it doesn't really do a whole lot of
harm as long as the rest of the gearbox is designed properly.
the problem is the combination of all three. the long input shaft
causes the case to flex under high load. as the case flexes it
pulls the first gears away from the driven shaft.

instead of the load being distributed completly across each
tooth of a gear: as the input shaft pulls away, the gear slides
away from the gears on the driven shaft. as it moves away, less
surface area on the teeth are able to cope with the load. already
weak gears struggle to cope with the load, and the teeth
strip off the gears.

Well said.

If you study the failed gears from a 5MT you'll find that most break at the back of the tooth not the front.

If the input shaft was to flex in any way the failure should be at the front of the tooth not the back, and 2nd and 3rd gear would not be as suseptable to breakage as 1st would due to the support bearings.

If the case flexes it allows the gears to move apart from each other to give the input gear teeth enought leverage to break the driven gear's teeth at the rear of the tooth.

I do believe there is some input shaft flex but if it was the overwhelming causes of 5MT failure you would think that the 6MT having the same length input shaft would run into the same failures at the same loads and Subaru would have changed the design.

As for hardening the gears or lack of properly hardening on the stock gears. The gears in a transmission or an axle have to be hardened in a way to make them hard enough on the outside to prevent wear but soft enough to take shock with out fracturing. It's a very tedious and exact process.

In the end it's not how hard the stock gear is or isn't that contributes to failure, it's a combination of the above mentioned issues.

I think the one thing we all agree on is that the 5MT could use a redisign. ;)

-Dylan

I wonder how much a person could recoup from a MRT/Kaaz/gimme /6MT buildup by selling the old tranny/diffs/driveshafts/shifters,ect. Rallispec sells the 6mt+install kit for $7100. I'd be you could recoup $1000-$2000 of that if the 5mt was in perfect shape for resale with low miles.

Originally posted by Zornorph
I wonder how much a person could recoup from a MRT/Kaaz/gimme /6MT buildup by selling the old tranny/diffs/driveshafts/shifters,ect. Rallispec sells the 6mt+install kit for $7100. I'd be you could recoup $1000-$2000 of that if the 5mt was in perfect shape for resale with low miles.

Well, the problem is the Kaaz and Gimmies are gearsets only, so you'd be using your old case, diffs, driveshafts, etc. The only thing you could really resell would be the old gearset which would probably not get you terribly much. Feel free to correct me on anything.

Originally posted by gjhsu


Well, the problem is the Kaaz and Gimmies are gearsets only, so you'd be using your old case, diffs, driveshafts, etc. The only thing you could really resell would be the old gearset which would probably not get you terribly much. Feel free to correct me on anything.

that kaaz is just a gear set... where as gimmies has a new imput shaft... at least i think thats what i read in the issue of turbo. If you want to drag your car you are much better off getting one of thoes new fangled autos, other wise there realy isnt a need for all the power were talking about here. My tranny does fine at 280+lbs.

I think the one thing we all agree on is that the 5MT could use a redisign

I do agree... and so does subaru. The new legacy has a redsigned 5 speed acording to the reports ive read.

HMM. Does it fit the WRX? Need more info. Where should I look on that.

Of the gearboxes, the new 5-EAT is the star attraction we feel. However, the heavily revised five speed manual is very much improved over the old model's, and deserves some attention. For one, the rotational mass of each component was reviewed and interaction optimised to minimise noise and vibration. Additionally, the internal workings and shift mechanism were redesigned to minimise friction for a smoother feel and less notchiness. Dual mass flywheels are used across the range for crisp response at all engine speeds... components, but Subaru has gone a bit further than many makers and over 90% of this car is new

http://www.apexjapan.com



It looks like a good thing... the car also has revised stearing rack, revised control arms, and among a crap load of other things the avcs now controls the exhaust side as well as the intake side:devil:

Great things comming to subarus near you... I wonder if I could use the brake booster off this thing, after my v7heads, 2.2 block, and new legacy tranny:lol:, Im going to need it.

well I looked at the MRT gearset, it's nice. goes for about $4400
US.

the major problem I have with it though: the noise. the Kaaz
gearset at least has 4th and 5th as synchromesh, and 1-3rd
as dog engagement, right? or is all the gears synchromesh?

It's not too informative on the site. anyways, MRT is more for
all out racing or running it at the strip. Kaaz is more suitable
for street use.

Already been talked about.

I hope this link will shed some mroe light for you. :)

http://forums.nasioc.com/forums/showthread.php?s=&threadid=315737&highlight=If+you+build+it

Cheers

Look Here (http://forums.nasioc.com/forums/showthread.php?s=&threadid=378667) As well. You can find the MRT gearset for $3100. It is available in all manner of speaking. Synchro, dog and combination if you wish. Have you seen a comparo of the Gimmie to stock. Have a look (http://www.freebmw.net/Share/CarsBoatsBikes/Subaru/GimmieGears/) . Helical as well, but beefy, great material. Quiet. By the way, those are cut by the same guy that cuts MRT. All synchro.

At this point, the Legacy tranny is on the top of my list. Much to be found out though. I wonder if they stuck or will stick it in the WRX? I am going to check the 04 legacy part number against the 04 WRX on Monday. Unless this is an 05 item not available yet. I'll look into it. Thanks for the tip. Very helpfull.

Need4Boost, are you still on stock GB too?:eek:

Here is what edmunds says. 05 features for sure.
Not only did Subaru release official photos of the next-generation Legacy wagon, we also managed to snag one of the first pics of an Outback prototype based on the same design. The standard Legacy will continue to use the current 2.5-liter boxer engine while an all-new turbo model will debut with a detuned version of the STi motor offering roughly 280 horsepower.
MUWAHAHAHAHA. Looks like I will be driving a Legacy WRX. Nah, will sell before that I suspect. Well, unless parts and conversion is reasonable. Damn. I am driving a dinasour already and it is only 3 months old. Doh!

Originally posted by ebeck

Need4Boost, are you still on stock GB too?:eek:

When I had the 16G I was. Now that I have moved on to the T3/T04E.... I still am. hehe. ;)

I plan on doing some upgrades, just when the time comes. :)

Still selecting my options.

Originally posted by Zornorph
I wonder how much a person could recoup from a MRT/Kaaz/gimme /6MT buildup by selling the old tranny/diffs/driveshafts/shifters,ect. Rallispec sells the 6mt+install kit for $7100. I'd be you could recoup $1000-$2000 of that if the 5mt was in perfect shape for resale with low miles.

I wasn't going to post prices due to upseting vendors but here is the lowdown (Mods feel free to edit post if Vendor complains)

I get pretty much brand new 6MTs for $4650 and the rest of the parts to install it with your R160 diff for $1250.

You could stand to recover about $1200 if your 5MT is still intact and you have the s.t. shifter and a good clutch (try and find a SVX guy to buy it ;) ).

-Dylan

I'm just looking at the 5MT and 6MT FSMs and it looks like the 6MT also has the long, unsupported mainshaft with only an oil seal at the front. Very interesting. The case is significantly beefier though. I had been thinking of having a bearing placed at the front oil seal, but maybe that wouldn't accomplish anything?

I'm getting my entire 2003 drivetrain for that price... Hrm.. a transmission worth more that the sum of the parts.

-Jon

stimpy, in my opinion, yes it would help. Especially with that long spindly shaft. No question. This has been brought up before. I wonder how hard it is to do. I know there are some professional mechanics that have these cases laying around. I see them on the forum. Perhaps one of them has an idea? Perhaps a new topic. "Why not add a bearing at oil seal with 5MT?"

I'll bring this up with Trey Cobb next time I'm down there. I know those guys have access to some incredible machine shops. It's just a matter of if it is finanically feasible to have the machine done and the bearing sourced.

-Jon

Originally posted by ebeck
stimpy, in my opinion, yes it would help. Especially with that long spindly shaft. No question. This has been brought up before. I wonder how hard it is to do. I know there are some professional mechanics that have these cases laying around. I see them on the forum. Perhaps one of them has an idea? Perhaps a new topic. "Why not add a bearing at oil seal with 5MT?"

I'll pull one of my 5MTs out and see if there is enough room for a bearing. I also have a bearing supply company near by so I'm wondering if i could get one to just "slip" in ??

-Dylan

downshift1, you are awsome. stimpy, Right on. Just curious Dylan, bearing, help no help?

not to steal your thunder or anything, but out of curiosity, how will you know if this added bearing actually fixes anything? Do you plan to measure shaft deflection with/without the bearing? Even if it decreases deflection, how will you know that it will prevent or reduce the chance of the tranny failing?

Guess some of us have to be willing to take chances for the benefit of the whole, I hope it works out!!

One small bearing for downshift1, one giant leap for Subarukind:lol:

Um, I don't. Better than sitting around complaining though. I thought about it last night, hard, not so sure. Stronger shaft is a must. Bearing 2 inches from where it connects to the engine. Not so sure. Can't hurt though. I have said it before, What do I know.

Took a 5MT apart last night, doesnt look like its going to work.

The bearing would have to be around 6mm thick, wich would have to be needle syle and require some form of lubrication.

Another issue is that the input shaft itself would have to be machined to a flat surface in order to provide assured straightness for the bearing.

I'm still looking at different options but I think it's going to be harder than it sounds.

-Dylan

Originally posted by downshift1

The bearing would have to be around 6mm thick, wich would have to be needle syle and require some form of lubrication.

Another issue is that the input shaft itself would have to be machined to a flat surface in order to provide assured straightness for the bearing.


What about a sealed needle bearing (ala the clutch release bearing, but with needle vs. roller or thrust)? You could design the outer race with tabs to hold it in the hole to either side of the case since it won't actually be getting a thrust load, only axial.

/Andrew

Originally posted by Kha0S


What about a sealed needle bearing (ala the clutch release bearing, but with needle vs. roller or thrust)? You could design the outer race with tabs to hold it in the hole to either side of the case since it won't actually be getting a thrust load, only axial.

/Andrew

I was thinking along that same line. I'm looking it to it tonight.

-Dylan

I know you can source bearings with a groove cut into the outside of the outer race for a snap ring. If they make them with two grooves the correct distance apart the snap rings could be used to axially locate the bearing with no extra machining to the case, simply slide on the shaft and re assemble the case halves. Should be able to get a bearing in a permanently sealed and lubed form as well. HTH's -Chuck

Originally posted by ataac_flat04
I know you can source bearings with a groove cut into the outside of the outer race for a snap ring. If they make them with two grooves the correct distance apart the snap rings could be used to axially locate the bearing with no extra machining to the case, simply slide on the shaft and re assemble the case halves. Should be able to get a bearing in a permanently sealed and lubed form as well. HTH's -Chuck

It's not so much locating the bearing in the case as it is getting a proper surface on the shaft without further comprimising the integreity of the shaft. I have found a bearing that will work (needle style, teflon sealed), but the shaft now becomes an issue because only certian sufaces are machined and the rest is left rough cast.

-Dylan

are you talking about a bearing whose needles are rolling on the shaft itself? Is there no room for a bearing with an inner race, therefore the shaft quality itself is less crucial? Forgive me if my ignorance of the exact inner specs of the tranny are lacking.

Just a note : Gimmiegears come from Aus. I don't know who makes them maybe par?

Zornorph... what Dylan is saying is that the shaft would need to have a section surface ground for the inner bearing race to either slide or press on to. You can't just slide a bearing onto a shaft (that's not prepped for a bearing) even with an inner race. What he's saying is that aside from splitting the case, we would have to disassemble the gearset to at least be able to remove the input shaft and have dimensions to give to a machinist to have the shaft "smoothed" where the bearing would ride. The process of having it machined wouldn't be all that difficult to have done, theoretically any machine shop that can grind crankshafts should be able to surface grind a small section of an input shaft for cheap (i.e. <$100, prolly less). But again the question of the day is : will it be worth the time/ energy/money to do it, and can the average joe split open his trans, disect the input shaft, install a bearing and put it all back into working order without special tools? -Chuck

Originally posted by ataac_flat04
Zornorph... what Dylan is saying is that the shaft would need to have a section surface ground for the inner bearing race to either slide or press on to. You can't just slide a bearing onto a shaft (that's not prepped for a bearing) even with an inner race. What he's saying is that aside from splitting the case, we would have to disassemble the gearset to at least be able to remove the input shaft and have dimensions to give to a machinist to have the shaft "smoothed" where the bearing would ride. The process of having it machined wouldn't be all that difficult to have done, theoretically any machine shop that can grind crankshafts should be able to surface grind a small section of an input shaft for cheap (i.e. <$100, prolly less). But again the question of the day is : will it be worth the time/ energy/money to do it, and can the average joe split open his trans, disect the input shaft, install a bearing and put it all back into working order without special tools? -Chuck

Well worded!

I'm thinking that this project would only be reasonable to someone using an aftermarket gear set in a stock case who wants an extra ounce of security with extreme power (350whp+). Between the labor to tear down the trans and dissasemble it (special tools required $250), have the input shaft machined correctly ($100), and have the whole dang thing put back together you're probably talking 10-14 hours ($900- 1500) in labor at a shop or the dealer. That's a lot of money to test a theory. :p

-Dylan

Dylan... Been looking at some of the pics on FreeBMW's site when he replaced his set with the Gimme Gears. Judging from the pics there, (for instance (http://www.freebmw.net/Share/CarsBoatsBikes/Subaru/GimmieGears/Install/IMG_5392.JPG) ) it looks as though the input shaft is already surface ground where the seal goes. A person would still have to take the main input shaft out of the trans case to slip the bearing on, but I don't understand why we would need the shaft machined for surface finish. And what kind of special tools might a person need for reassembly. Are we just talking about some feeler guages or a dial indicator? or some specialty tool to correctly line up the shifter forks a certain way so you can assemble the case halves? If they are needed for bearing clearances, why can't a person reassemble with the same amount of shims that originally came out (assuming the trans hasn't failed). Just points to ponder for those of us still on the cheap. :) I'm thinking this is something I can do myself, hence the questions. Even though I have never actually seen the innards of this type of trans (sans pictures) -Chuck

Originally posted by ataac_flat04
Dylan... Been looking at some of the pics on FreeBMW's site when he replaced his set with the Gimme Gears. Judging from the pics there, (for instance (http://www.freebmw.net/Share/CarsBoatsBikes/Subaru/GimmieGears/Install/IMG_5392.JPG) ) it looks as though the input shaft is already surface ground where the seal goes. A person would still have to take the main input shaft out of the trans case to slip the bearing on, but I don't understand why we would need the shaft machined for surface finish. And what kind of special tools might a person need for reassembly. Are we just talking about some feeler guages or a dial indicator? or some specialty tool to correctly line up the shifter forks a certain way so you can assemble the case halves? If they are needed for bearing clearances, why can't a person reassemble with the same amount of shims that originally came out (assuming the trans hasn't failed). Just points to ponder for those of us still on the cheap. :) I'm thinking this is something I can do myself, hence the questions. Even though I have never actually seen the innards of this type of trans (sans pictures) -Chuck

There are 2 special sockets that you need to dissasemble the two shafts. They are only available through Subaru (I've tried Snap-on, Matco, & MAC). Along with that you'll need the dial indicator and feeler gauges. The surface that is machined for the seal is at a point in the case where there is not much support and may cause a fracture of the case under load. I would like to see someone try it, just to see if it works, but for me it's just not worth the time. ;)

-Dylan

Maybe I was mistaken on the location of the extra bearing in question then. Where are you thinking of putting it? :confused: -Chuck