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01-21-2009, 01:51 PM | #251 |
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Good points! No, I never completely dismissed case flex either but decided that it must be just one small component of many in the whole picture rather than the smoking gun of why these gearboxes fail. You are right on about the case changes...obviously they were looking for ways to increase rigidity and they wouldn't be spending more money on bolts and machining if there was no reason to do so. And if you look at the 6-speed you see a complete revolution in the case design, one part of which is the elimination of the longitudinally split case and the other is the introduction of a thick steel shaft support plate. I think also the bellhousing casting thickness is increased in some places as well.
Good overview on the shockloading aspect also! It gives you some idea of how much affect a very aggressive clutch design (one with very little slip) can have on the gears in a hard launch. We've always tried to steer people in the direction of an organic clutch with the 5-speeds whenever the torque levels and application didn't demand going with something more robust. A side point I'd like to make....very frequently people tell us they were not doing anything crazy when their gears let go. However most often the failures originate at some earlier point during a hard launch or agressive shift. Small cracks form at the roots of the teeth engaged at the time of the shockload. These cracks continue to propogate over time until finally the teeth let go. So just because the gears failed during normal driving doesn't mean they were not compromised at some earlier point during some more aggressive driving.
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01-21-2009, 05:59 PM | #252 | |
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01-22-2009, 01:22 PM | #253 | |
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A couple thousandths of an inch in gear lash can be the difference between a transmission that lasts 200,000 miles and one that wears down and fails in say 30,000 miles or less... So when all of these small factors are stacked together, it doesn't take much to put undue strain on the gears. In whatever gear, when the clutch is engaged violently, failure can either be immediate or a small microscopic crack can appear which over time propogates/grows from fatigue (repeated back and forth flex in metal) and causes the gear to fail at some point in the future. The logic of course, is that since there are multiple factors involved, anything we can do to patch up one weak spot may help overall by contibuting less to gear seperation. Even very strong aftermarket gears are subjected to the same problems that the stock gearset has to deal with... The big difference is that PPGs, for example, are allowed a rather aggresive/large tooth profile at the cost of increased noise, so the gear teeth are just so big that they can cope with a larger amount of seperation than the stock gears can handle and the customers that buy them don't really tend to mind the noise. Could Subaru have made gears similar to PPG's product? Sure they could, but even PPG's helical tooth profile would be far too loud to put in a production car, and smaller more numerous gear teeth for any given centerline spacing tend to be slightly more efficient at transfering power. Last edited by jhargis; 01-22-2009 at 01:31 PM. |
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01-25-2009, 04:18 PM | #254 |
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good info in this thread. keep up the awesome work.
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01-28-2009, 06:57 AM | #255 |
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I saw that the website was updated. Everything looks like it's coming along nicely. I'm looking forward to seeing what the diff brace will look like.
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01-28-2009, 11:07 AM | #256 | |
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I finally got around to getting the Nighthawk website up to par... That site has kinda been in limbo for a couple of months while I've been working on the production side of things. Due to recent happenings, I'm pretty much the only person running the factory floor at the day job. And on top of it, I'm still trying to keep up with everything for Nighthawk, so life has been all kinds of busy lately. Here's the brace: I haven't talked to Dylan about it yet, but I think I'll be dropping the idea of a passenger's side diff brace. I don't think I can come up with anything that will be effective and affordable at the same time. There's no super convenient pre-drilled boss to bolt the thing into like there is on the driver's side. No matter really... A passenger's side brace would be nice for the really high horsepower guys as an added reinforcement, but the driver's side brace covers the part of the diff housing that flexes really badly. Last edited by jhargis; 01-28-2009 at 11:22 AM. |
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01-28-2009, 06:39 PM | #257 |
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Yea, I could see that as well. Especially with the downpipe being there anyway - it may be hard to make a universal brace that works with all downpipes.
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01-28-2009, 09:34 PM | #258 |
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^^^ That's exactly what I was having problems with, I'd have to keep it really snug up against the transmission to clear the pipe, and the only place to bolt anything to is the threaded hole where the stock downpipe support bracket bolts to, which is actually into a fairly thick piece of of the case structure that doesn't need reinforcement as badly as the other side anyway.
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01-30-2009, 12:01 AM | #259 |
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Jhargis, what about building a two piece frame that encases the transmission housing? One half goes on from the top and the other from the bottom. You could use steel tubing and put a ring plate around the outside of the front diff adjusters, pressed against the transmission. This type of brace would have to be installed with the trans out of the car of course. Maybe using several smaller steel tubes with integrated "x" patterns here and there would allow more attachment points. Would you be able to make one unit and form a jig around the test unit to produce the others? Just a thought.
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01-30-2009, 12:29 AM | #260 |
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That was one thought that I kicked around a bit earlier on until I took some measurements and rough calculations of cost. In fact, I had originally envisioned having the frame structure extend back to the center diff section of the case the strengthen that area as well.
Alas, it would be very difficult to get a cage structure to fit inside the trans tunnel and clear the downpipe, the plate only allows just enough clearance as it is and it gets prety tight back there toward the rear of the transmission. Also, who wants to spend $600 or more dollars on a case cage short of maybe the rare cost-is-no-object 5mt project guy? I'd have a hard time selling something so expensive and wouldn't be able to make very many of them because it would be pretty labor intensive. Thanks for the input though. It would be pretty cool, but I'm not sure if all the effort and cost would be worth it when 6mts are getting more affordable and easier to find. |
01-30-2009, 12:55 AM | #261 | |
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Yeah, exactly what I was talking about. Extending back to the rear housing would give maximum bolt locations as well. I think you could do it, and am sure you would get substantially less deflection if the two reinforcement halves overlapped eachother and shared several of the side bolt locations. C'mon.. you can do eet! Besides, the 6mt's aren't perfect either.
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01-30-2009, 02:02 AM | #262 |
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pm me when this is finalized and I will be more then happy to install on my 06wrx with ppg's and post my reviews.
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02-04-2009, 10:15 AM | #263 |
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so when would the finished product will be availabe for sale???
how much is it gonna cost??? |
02-04-2009, 01:20 PM | #264 | |
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-http://www.nighthawkautomotive.com/ <- look in the products section. The reinforcement plate is listed, and I'll have a page for the diff brace up probably in the next few days. Last edited by jhargis; 02-04-2009 at 01:28 PM. |
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02-04-2009, 09:17 PM | #265 |
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How about machining a plate that goes where they crack and weld it to a open case, then reassmble it? Wouldnt that be the ultimate solution?
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02-04-2009, 09:47 PM | #266 | |
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You also have to figure that the average mechanic or DIYer can install the diff brace with the transmission in the car in about 30 minutes using a ratchet, some sockets and a torque wrench. Dropping the transmission, taking the case apart and welding a plate in is something the average buyer is not going to want to do... In this case, I'm trying to keep things as simplified as possible for customers. |
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02-04-2009, 10:21 PM | #267 |
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keep us posted on price and availability I would like these for my 07 when i get my clutch and PPG's done
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02-05-2009, 07:19 AM | #268 |
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What about a possible transmission cooler? I know it's hard to weld to the stock aluminum case as well, but what about just drilling and tapping so that another fitting can be added as a return/feed line?
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02-05-2009, 10:42 AM | #269 | |
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02-05-2009, 11:24 AM | #270 | |
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True, compared to the size of the case as a whole, it doesn't seem like a gigantic change... But take for example, that the webbing on the case (the thin vertical structures in the case that spread out from the axle stubs) look fairly insignifcant as well, but they add a lot of stregnth to a case because they are located strategically at just the right spots. Notice that my brace bolts to a location that does not have much external webbing, and just to left of where the brace fastens in that picture is where the case tends to crack Last edited by jhargis; 02-05-2009 at 11:29 AM. |
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02-05-2009, 12:10 PM | #271 |
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I am ready to buy, just say when.[06/wrx]
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02-05-2009, 01:39 PM | #272 |
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02-05-2009, 02:02 PM | #273 |
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Very interested in buying this when they come out
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02-05-2009, 02:43 PM | #274 |
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yes i also want it
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02-21-2009, 11:40 AM | #275 |
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Where is this product now?
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