6MT spec b vs STI trans

[NSFW]

Nope... Pedal effort is about the same as stock, and the clutch slips well enough for stop-and-go stuff. It's different enough that it took me some time to learn to drive smoothly with it, but after that it has been no big deal.

[BAC5.2]

Two things:

 

1) An open front diff won't keep the fronts from spinning. The opposite, in fact, is what happens. Ask anyone who has a 5MT with the Cusco Tarmac diff. Spin the wheels, and the fronts unload. An open diff WILL keep you from snapping all 4 axles, though. Barring axle breakage, you will always out-launch an open diff with a locked diff. Look at the DSM guys. The ones that crack off sub 1.4' 60' times on street legal tires, do it with welded diffs. Shep runs 7.70's with a spool.

 

2) NSFW launches exactly right. Revs up, quick release of the clutch, spin the tires, and go. It doesn't get any faster, or more reliable, than that. Traction is what breaks things. A little wheelspin off the line, and you are golden. Launch hard without wheel spin, and you'll kick out an axle.

 

I have never seen anyone break all 4 axles on a single launch. I have seen one of the faster auto-x cars around here launch at an event (in LOCK, on hot Hoosiers), heard a loud bang, then saw one of the rear axles roll out from under the car (snapped at both splines). IIRC that car made almost 500 ft-lbs.

 

A Spec-B center diff won't handle 500+whp on a hard launch. You'll just spin the fronts, and eventually pop the center diff.

[StoplightAssassin]

I have never seen anyone break all 4 axles on a single launch. I have seen one of the faster auto-x cars around here launch at an event (in LOCK, on hot Hoosiers), heard a loud bang, then saw one of the rear axles roll out from under the car (snapped at both splines). IIRC that car made almost 500 ft-lbs.

 

He's stage 2.

 

...and actually broke both rear axles.

[BAC5.2]

He's stage 2.

 

...and actually broke both rear axles.

 

What?

[StoplightAssassin]

What?

 

You're talking about whitetiger correct?

[ShadowImg]

If we're talking about whitetiger, it's also a 5MT with a front LSD.

[whitetiger]

^yes i did that. both rear axles in 1 hole shot at the NNJR Pro Solo event on the second day.

[BAC5.2]

You're talking about whitetiger correct?

 

No.

 

I'm talking about a local. A 93 Impreza with a built 2.5, 2L shimless heads, and a 6MT. He made something near 500ft-lbs and one of my former coworkers spit an axle on a hard, locked-on-hoosiers launch.

[StoplightAssassin]

oh lol.

 

almost the same exact story

[BAC5.2]

Except it was only one axle, and it was an R180 axle.

 

Regardless, if you want to launch like that it's going to cost you somewhere. That somewhere can be your wallet (in the form of breakage or upgrades) or your time slip.

 

I've NEVER seen all 4 axles break on a launch.

[whitetiger]

for me, i was doing hard launches all day with an upgraded rear diff and 255 wide hoosier A6's. if i were doing it with the stock rear r160 VLSD diff, i would have blown that up instead.

[ruggerheist]

No.

 

I'm talking about a local. A 93 Impreza with a built 2.5, 2L shimless heads, and a 6MT. He made something near 500ft-lbs and one of my former coworkers spit an axle on a hard, locked-on-hoosiers launch.

 

thats the engine build im doing. im not machining my heads though, going with big valves instead. are there any options for stronger axels? i have YET to come across anything

[ShadowImg]

Honestly, if you're running that kind of power, and you're racing competitively, I would think the cost of replacing an axle would be kind of on the "acceptable losses" list.

 

If you run stronger axles, there's just going to be a "next weakest link". Pick the one that you are most willing to sacrifice.

[ruggerheist]

point accepted

[NSFW]

Yeah, the term is "mechanical fuse." Something whose job is to blow, so that something more expensive won't blow.

 

MSI can get upgraded spec B axles get from Albins, but first they want some details about the stock axle shaft... Diameters, spline counts, etc. I was going to buy one for reference, but then decided yo buy two instead, and just keep them on hand when I race. I don't know what will break of the axles don't, and I don't think I want to find out. Axles are not cheap, but at least they are not hard to replace.

 

Edit: next step: build a list of needed tools, to keep in box with axles... maybe....

[NSFW]

Btw, regarding guy I mentioned earlier... I don't recall how many axles he was breaking at once, but I think if he'd blown all four at once, that probably would have stayed with me.

 

I do remember E85 and 500 ft/lb though. Not sure if crank or wheel, but probably wheel. Which also means axle.

[BAC5.2]

Yeah, the term is "mechanical fuse." Something whose job is to blow, so that something more expensive won't blow.

 

MSI can get upgraded spec B axles get from Albins, but first they want some details about the stock axle shaft... Diameters, spline counts, etc. I was going to buy one for reference, but then decided yo buy two instead, and just keep them on hand when I race. I don't know what will break of the axles don't, and I don't think I want to find out. Axles are not cheap, but at least they are not hard to replace.

 

Edit: next step: build a list of needed tools, to keep in box with axles... maybe....

 

A 32mm socket, some 19's and some 17's should do the trick. Plus a giant ass breaker bar.

 

If you want custom axles, I'd call DriveShaftShop before calling MSI. At least the guys at DSS are honest.

[NSFW]

This thread turned me off of DSS completely:

http://forums.nasioc.com/forums/showthread.php?t=1587952

 

I'm generally not a sucker for "I heard bad things about..." but when Turn In Concepts, KartBoy, and Rallispec all report problems with one manufacturer, I can't ignore that. Plus one random guy who reports that his DSS axles have slop and make noise.

 

Haven't decided yet whether to upgrade my axles or not, but at the moment I'm leaning toward doing it. Been reading threads about stock 6MTs running 10s, which makes me think that if I upgrade my axles, maybe the next thing to fail will just be traction. I'm pretty sure I'm going to blow a stock axle eventually, I guess I'll make up my mind when that happens.

[NSFW]

Two things:

 

1) An open front diff won't keep the fronts from spinning. The opposite, in fact, is what happens. Ask anyone who has a 5MT with the Cusco Tarmac diff. Spin the wheels, and the fronts unload.

 

Just for the record, everywhere I mentioned an open diff earlier, I was referring strictly to the center diffs. But I can see how spinning the rears would depend on the front diff too, I hadn't thought of that.

 

Seems like one more point in favor of swapping to an STI 6MT - far as I know, none of them have open front diffs. (USDM anyway - I have no idea about JDM.)

[NSFW]

Its misleading to say AWD does not give you "better launches". Better launches than what? A trailer queen RWD on Hoosier race slicks? AWD does give a "better" launch, but better than WHAT exactly. A hell of a lot better than FWD anyhow.

 

Really fast drag cars have really fast suspension setups that keep the drive wheels on the ground and making contact. Anyhow, remove squat from the rear = more weight on the front wheels.

 

Found this while searching for that DSS thread I linked to earlier:

 

http://forums.nasioc.com/forums/showthread.php?t=2141957&highlight=dss+axles

[fahr_side]

A 32mm socket, some 19's and some 17's should do the trick. Plus a giant ass breaker bar.

My buddy just had to remove an axle. Took a 1" drive air impact hammer to get the nut off, the kind they use on semis... :O That's the other consequence of big drive torque.. it also tightens the axle nuts.

[BAC5.2]

This thread turned me off of DSS completely:

http://forums.nasioc.com/forums/showthread.php?t=1587952

 

I'm generally not a sucker for "I heard bad things about..." but when Turn In Concepts, KartBoy, and Rallispec all report problems with one manufacturer, I can't ignore that. Plus one random guy who reports that his DSS axles have slop and make noise.

 

Haven't decided yet whether to upgrade my axles or not, but at the moment I'm leaning toward doing it. Been reading threads about stock 6MTs running 10s, which makes me think that if I upgrade my axles, maybe the next thing to fail will just be traction. I'm pretty sure I'm going to blow a stock axle eventually, I guess I'll make up my mind when that happens.

 

You do have to take that thread with a grain of salt. Look at reply #16. Would you really trust anything Dylan @ DS1 has to say? He thought Kartboy Short Shifters caused selector shaft seals to leak, and he thought Porsche designed the Subaru 6MT.

 

I've had good luck with their Subaru stuff. Sometimes it isn't right, where they send the wrong parts or something, but when you get something that fits the quality is pretty good. I wouldn't use one of their driveshafts, though. I'd just buck up and go ACPT.

 

IMO, it would be worth it to call them and talk about bar upgrades for the Spec-B. They are cheap, and they work well. The next failure, however, will be axle cups. If you spend lots of money, and do their full Level-5 setup

 

Your point about mechanical fuses is a good one. What's the next thing to go? Traction, possibly. But in reality, it'll be center diff transfer bearings. That's the Achilles heel of the 6MT, and something you really need to keep an ear open for. One of those bearings lets go, and goodbye 6MT.

[BAC5.2]

Just for the record, everywhere I mentioned an open diff earlier, I was referring strictly to the center diffs. But I can see how spinning the rears would depend on the front diff too, I hadn't thought of that.

 

Seems like one more point in favor of swapping to an STI 6MT - far as I know, none of them have open front diffs. (USDM anyway - I have no idea about JDM.)

 

I actually meant center diff, and I'm not sure why I put front. Still, an open front is a valid point too. An open front will encourage wheelspin, and you are correct that no USDM STi ever had an open front diff. The Spec-B does, though.

 

But I did mean center diff. An open center-diff will encourage the fronts to spin on launch, not unload to the rear. From a "break traction not axles" standpoint, this is a good thing. But wheelhop on a sticky track with a sticky set of tires is going to do a hell of a lot of damage.

 

While a VC diff isn't "open", it'll still unload the front wheels when overpowered.

[BAC5.2]

My buddy just had to remove an axle. Took a 1" drive air impact hammer to get the nut off, the kind they use on semis... :O That's the other consequence of big drive torque.. it also tightens the axle nuts.

 

A long breaker, and some courage will crack the nut free. Just brace the breaker on the ground, and roll the car backwards. I've never tried it, but I bet it would work. Might help to have a friend spotting.

 

Axle nuts shouldn't tighten if they are staked properly. I cant say I've ever seen that, even on the 600+whp cars I'm familiar with. I suppose it could happen, though.

[NSFW]

I already talked with DSS about an axle upgrade w/ shafts and joints, and they're happy to do it but they need information about the spec B axles first, same as MSI/Albins.

 

But I arrived at my decision without considering DS1's input in that thread. F***ing up the ABS on the Evo driveshafts, and then refusing to do anything about it, would be enough all by itself. Kartboy buying three driveshafts of different lengths would almost be enough. "Foolio" in that thread is the guy who overhauled my 6MT, and him having bad experiences with both a driveshaft and a set of axles would almost be enough. All together it's enough to steer me away. With that track record I'd rather gamble on a complete unknown.

 

Maybe they've gotten their shit together in the last thee years, but I don't want to blow $1200-$1500 to find out that they haven't. Especially considering that I'd be asking them to make their first set of spec B axles. Considering that they wouldn't fix the ABS rings on those Evo shafts, I wouldn't expect them to take me seriously if I tell them they don't fit right, or they're off by 3/8" (which, judging by Kartboy's experience, is their idea of an acceptable tolerance).