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enhance gears for the subaru WRX 1

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JUANMEDINA

JUANMEDINA

Mechanical
Joined
Nov 9, 2006
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US
As most of all you know the gears on the WRX transmission are really weak. In 06-07 WRXs the 3rd gear is specially weak and is the only one that fails. I'm just wondering what will take to make the 3rd OEM gear out something stronger like steel 9310? What will it happen to other gears? Do you know of any gear vendors that can do this?

thanks
 
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It will be very expensive. It's probably cheaper to upgrade to the 6-speed tranny.
 
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I really don't think It will be that expensive there is nothing to design. I think send the gears to machine shop get them measure on a CMM, make a CAD drawing, send the drawing to a machine shop with CNC and get the gears mill out of 9310 steel. There is a vendor that sells PPG gears they are made out of 9310 but they cost 5K, another vendor makes gear I think out 8620 but they are too weak they are only rated at 400wtq and they cost 2.5k. I'm not talking about just 1 gear for me, I'm talking about mass producing them. I know someone that wants to make this happen but he is having trouble finding a vendor. Do any of you know a gear vendor?

1-2 are really beefy, 3 is not, 4-5 are not a problem. I will have to make 3-4 because they are assemble together.

thaks
 
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thanks but that doesn't help me much and those gear are weak I don't even think they make them anymore.

I'm looking for input of what I want to do, I don't what to buy the whole tranny I want to fix what is breaking and go from there. Please help

Thanks
 
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Most machine shops are not equipped to make gears as precise or as strong as you need them to be. The few that are so equipped will probably have 'gear' in their name.

You unduly minimize the cost and risks of reverse engineering. It's not that easy, and a CMM doesn't make it easier.






Mike Halloran
Pembroke Pines, FL, USA
 
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Juan- I have had several discussions with many many people over the 6+ years I have owned my WRX. I am a metallurgist and materials scientist. There is almost no gain to be had by manufacturing a set of one off gears for the WRX 5 speed transmission. In this case the limiting factor of the transmission is not the gear material.

Two ways you can increase the life of the 5spd WRX transmission are:

1. go to dog cut gears, this will allow the gears to tolerate the higher misalignments present in the 5spd when at 2x the factory torque output.

2. Do NOT sidestep the clutch. Ever.

How did you select 9310 steel? why do you say its strong....

teh helical cut and involute tooth profiles require a multi Axis wire machine, then a full heat treating process, and finally finish grinding to provide the accuracy required.


you could expect to pay >$5000 for a one off part, made right........

nick


Nick
I love materials science!
 
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Good on Nick.

Hopefully sanity will prevail.

Regards
Pat
See FAQ731-376 for tips on use of eng-tips by professional engineers for professional engineers
 
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PPG are made of 9310, racing gear suppliers make gears on 8630 for regular racing applications, and 9310 for extreme racing applications.

Google is your friend

If MFactory made a close ratio gears with custom ratios and sell 1-5th with a main shaft made out of 8620 for about $2300. Why copying 3-4th gear and make it out of 9310 and mass produced will be more expensive?

Are you from NASIOC? why are people on that board so close minded? Is like when along time ago I make a thread about using E85 and they were like no is not worth it etc,y
Now if you go to EVOM a good number of cars are running E85 and making more power than car on meth and race gas lol. Soon my WRX with a VF39 will be on E85 and it will be faster than car runing 20gs and greens on pump gas lol. And when they say that VF39 will not make more power at 20psi, now the fastest ones are running 25psi and more safely.

Any ways I am looking for input on the process that I need to follow in order to make this happen. Also I am looking for gear vendor that maybe one of you guys know. Please don't make comments that this will not work that will be to expensive, let find this for myself.

Thanks

 
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Uh, "mass production" in the automotive world means several thousand cars or sets or parts... every working day.

Half a dozen custom gearsets is "small lot manufacture". There are guys who do this sort of stuff, but if you expect them to invest in tooling, you have to be able to show them that you'll be back, in a day or a week or a month for another half dozen... or you have to buy the tooling for them. It will make custom gears look cheap.

At this point, searching for suppliers is pointless; what you need first is _customers_, lots of them.



Mike Halloran
Pembroke Pines, FL, USA
 
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You have had good advice. You seem to resent it because it does not agree with your ideas. The people giving you that advice have a great deal of experience and knowledge.

My position now is you can have your money back.

No further comment.

Regards
Pat
See FAQ731-376 for tips on use of eng-tips by professional engineers for professional engineers
 
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If vendors are selling stronger gears out of 8620 and you're sure that 9310 is the ticket, why don't you talk to this vendor(s) about making you a set out of the 9310? It would likely only cost you the difference in materials plus their regular price and, maybe, they'll even cut you a deal as you'd be doing them some R&D testing by running the other material.
 
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Racing gears aren't always stronger than street gears. I think it's Richmond that makes rear end gears intended for drag cars out of a softer metal so they're less brittle and don't strip the teeth on a hard launch. They will wear out faster than the normal street gears however.
 
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Do the factory gears fail in fatigue or sudden failure? Look for beachmarks to indicate high cycle fatigue. I am not a metallurgist but was wondering if the gear could be re-heat treated to make it more plastic? Obviously not the ideal solution but tractor pullers have been known to do this when aftermarket gears are not available.

ISZ
 
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IceStationZebra-

The issue with the WRX transmission is more a design issue than a materials issue. The basic design is almost 30 years old. it was designed for motors whose torque output was ~50% of the 2.0l in my 2002 USWRX.

With the 2.5l motor in the current model the ability to modify for higher torque is verging on ridiculous. At these torque levels the case flex becomes severe, causing the stock helical cut gears to fail.

That said, the modern 6spd subaru transmission is from all reports, quite stout.

JuanMedina- There you go. If you do decide to go with a custom gearset I would reccommend using S7 tool steel hardened to ~55HRc. This would be an optimum material. The heat treat is far simpler than that required by 9310, a carburizing/nitriding grade. Also S7 was developed for shock loading, since you're likely a drag racer.

As an aside:

I have 160,000miles on the stock subaru 5spd. All I've ever needed to do is use good gear lube, Redline heavyshockproof w/75W90. I've competed in over 5000miles of "brisk" TSD Rally, and done some really silly stuff with this car. I have no problems with the synchros, gears, or shift linkage. I have blown the center diff viscous retaining ring, that happens after thousands of full throttle slippery surface starts. I will be replacing it with the more aggressive STi GrpN component soon. I love my WRX, and no You cant have her.


Nick
I love materials science!
 
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9310 carburized is chosen for toughness !Impact loads ,not strength per say.My thoughts were -you replace one part then another fails etc. But Nick E responded perfectly .Good engineering is always engineering of a system not just one part.If the gearbox is obsolete replace the whole thing .Drive on ! Rally New York
 
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If case flex is the problem than stronger gears are just a band-aid fix, though I do find this an unlikely cause. Looking at a picture of the transmission it seems more likely that the shafts allow too much flex as 3rd gear is in the middle of the support bearings. (From the picture it looks like 3rd might also be a little narrower than 2nd?)


ISZ
 
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From the above link:

What is the second biggest transmission misconception? Case flex occurs within Subaru transmissions.
 
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Ok, so if it isn't case flex, its shaft flex. Every failed gear I've seen shows no fatigue. They do show witness marks that are not appropriate for the tooth.



Anyway, for juan's purposes there is nothing short of unobtainium that can solve a gear breakage problem on a 5spd WRX transmission.

 
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