I bought a Modena front LSD

skid542 · Post by **skid542** » Fri Feb 13, 2009 5:05 am

As many of you know, I've been bitting the bullet and getting a nice 5mt put together for my SS and today I up'd the ante one more notch. I told them to put a new Modena helical front LSD into it while they're at it, what with the new mainshaft and triple ring syncro's and all.

I don't have any reviews to provide at this point - other than Matt's been taking great care of me. But it's finally really sinking in that I'm going to have a 'badass' 5mt and I just had to share the joy.

That is all

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93forestpearl · Post by **93forestpearl** » Fri Feb 13, 2009 5:17 am

Nice. My buddy has been eyeballing the Modena front diff for his highly built SS auto for quite some time.

A helical front diff is the shit. I like it as it helps steer the car under power. My beater wagon in the snow just isn't as much fun.

Adam West · Post by **Adam West** » Fri Feb 13, 2009 11:57 pm

Can you post link to dif? And detail what special sauce is in your 5MT rebuild?

Matt Monson · Post by **Matt Monson** » Sat Feb 14, 2009 12:26 am

They aren't making them anymore. I've got a handful of the last of them that were made before they went to strictly 6 speed stuff. I'll post a picture later. I don't think you'll find them anywhere else on the interweb for sale. I also have what is probably the last 5spd straight cut dog box kit they cut before they quit production.

93forestpearl · Post by **93forestpearl** » Sat Feb 14, 2009 8:59 am

^ I''l let my friend know about that. Do you have any of the auto diffs left?

skid542 · Post by **skid542** » Sat Feb 14, 2009 8:51 pm

Adam, I don't have any special sauce, just a special tranny

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Basically it's a 02' WRX tranny that Matt is installing a new mainshaft into that has the LGT 1-2 gears. This reduces the RPM lag going from 1-2 normally that the WRX has. Additionally, the LGT 1-2 gears are also known to be the same as the STi, non RA, gears. So they should be nice and strong and able to hold my 300 chp goal (for right now). Matt is also putting in somenew synchros. And then I told Matt to go ahead and install this new LSD up front. So I will have helical up front, VSLD in the center, and VSLD in the rear. It's going to rock

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Adam West · Post by **Adam West** » Sun Feb 15, 2009 4:08 am

Interesting...so what will be your gear ratios and final drive? This tranny spec is to benefit autocross applications or drag racing? And what changes to reinstall will you have to make to accommodate the center diff?

What will you be doing for clutch and flywheel?

skid542 · Post by **skid542** » Sun Feb 15, 2009 6:31 pm

The final drive will be 3.9. The gear ratios will be similar to the WRX except 1-2 will be a little taller.

The tranny is being built for daily driving and Auto-X. I don't really care about drag. One day I'll have to go out to the stip just to see what it does, but it's a curiousity reallyu.

The center diff is not changing. It's the front diff. The center diff is still the standard 5mt VSLD. In order to swap out the front, there's nothing special required - just some know-how. Matt would be able to answer that more than me. However, as I understand it this unit was made for the Subaru 5mt and is pretty much a drop in replacement. As far as installing all this coolness, it's just a basic 4eat->5mt swap.

My clutch is a stock WRX unit from Excedy and my flywheel is ACT's Streetlite flywheel, around 13lbs. All brand new along with new Grp N tranny/engine mounts.

tahoe.ss · Post by **tahoe.ss** » Sun Feb 15, 2009 9:42 pm

hey skid, what is VSLD? i'm new to the all wheel drive stuff?

Adam West · Post by **Adam West** » Sun Feb 15, 2009 10:45 pm

Uhhh...

http://en.wikipedia.org/wiki/Limited_slip_differential

Lee, that's cool. Best of both worlds on the gearing. I had a 99LGT and I really like first and second but fifth was too short and droned a bit.

Cheers and let us know how it drives when you get it in.

~AW

GodSquadMandrake · Post by **GodSquadMandrake** » Sat Feb 28, 2009 6:54 am

I'm curious to see your impressions on what this does to the balance of the car. I have heard some people say that with the stock center diff an LSD in the front causes a lot of understeer and takes away from the car's balance. I can see it vastly improving front end grip but without DCCD it may make it more like a FWD car. I'm not trying to rain on your parade if that's what you want, everybody wants something different. For autocross I'm sure the front LSD will be a big help. For just messing around in the snow I like the open front diff and LSD rear diff option myself.

skid542 · Post by **skid542** » Sat Feb 28, 2009 7:08 am

^^^ I'm anxious too. The tranny's in route to me now

.

I'm a little confused by your comments though. If it vastly increases front end grip, how does it induce more understeer? And a DCCD in 50/50 mode isn't really any different than the stock center diff. You can get just about any car into an understeer situation if you don't drive it correctly, but I'm still inclined this is really going to help.

Keep in mind that I will also have a rear LSD as well. This is essentially the same setup as the 6spd STi's have, except I don't have the center adjustability. But most of the people I know keep their's at 50/50 most of the time anyhow.

Now if I were throwing in a plate/clutch front LSD then I'd have more concern about balance, but the helical should work great.

And as far as the snow, if it's slick enough the helical front diff will act like an open anyhow. I love the rear LSD in my OBW in the snow and can't see how this can be any less fun - let alone when I have enough traction to get the front to transfer power - it's going to be glorious

.

Anyrate, I will definately post my reviews. First day of testing/tuning on the autocross course occurs in April though I'll have initial reviews up before then.

T minus one week

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93forestpearl · Post by **93forestpearl** » Sat Feb 28, 2009 8:58 am

50/50 with a DCCD center is essentially locked, so its not quite the same as a viscous center. A DCCD diff is actually very similar to the tranfer clutch in an auto trans, except it is actuated by an electro magnet vs hydraulic pressure.

skid542 · Post by **skid542** » Sat Feb 28, 2009 4:13 pm

^^^ Fair enough.

GodSquadMandrake · Post by **GodSquadMandrake** » Mon Mar 02, 2009 2:13 pm

Maybe it wouldn't increase understeer, but reduce oversteer.

Matt Monson · Post by **Matt Monson** » Thu Mar 05, 2009 3:09 am

skid542 wrote:
Now if I were throwing in a plate/clutch front LSD then I'd have more concern about balance, but the helical should work great.

And as far as the snow, if it's slick enough the helical front diff will act like an open anyhow. I love the rear LSD in my OBW in the snow and can't see how this can be any less fun - let alone when I have enough traction to get the front to transfer power - it's going to be glorious .

That's correct. Since it's not a clutch type LSD it won't have the same positive locking that one of those would. That's why Subaru uses torsen style differentials on the factory high performance cars.

A clutch style lSD effectively locks the spin of the two wheels, and even though it allows limited slip, it still hooks them together, which, when on the front wheels will fight turn in and cause the car to understeer.

The torque biasing differential on the other hand allows a greater speed differential between the two wheels. It doesn't benefit you quite as much in assisting your braking, but like a clutch type LSD, it allows you to get on the gas sooner and pull your way through the corner. It's from that ability to go positive throttle earlier that will make the car lap faster.

Lastly, the gears that we put in Lee's car are as follows:

3.166 1st
1.882 2nd
1.296 3rd
0.972 4th

5th was left stock at 0.735

Over on NASIOC guys are calling these LGT gears. I consider that a bit of a misnomer. While the 2004 LGT was the first time we here in the states saw these ratios used, they were originally introduced in the V5 STi and continued through the v6 STi and Prodrive P1, but with a super short ring and pinion of 4.44. In fact, Rallispec has been selling these ratios for years as just that, STi stree ratios, at a slightly lower price than their RA gears. They are also the same ratios found in my 2008 WRX, except in that car we get a shorter 0.78 5th gear.

If you guys want to see some comparative gearcharts, I have them on excel spreadsheets. I just have no way to convert them to a Jpeg and host them. If some computer guru wants to reformat them and host them that would be very much appreciated.

brand · Post by **brand** » Thu Mar 05, 2009 3:25 am

Matt Monson wrote:I have them on excel spreadsheets. I just have no way to convert them to a Jpeg and host them. If some computer guru wants to reformat them and host them that would be very much appreciated.

I can post them (brawest@gmail.com). Another good option is a google document that's accessible to everyone. If you send em to me I can post a link to the excel sheet, an image, pdf, whatever.

skid542 · Post by **skid542** » Thu Mar 05, 2009 4:24 am

Here's a screen print of the spreadsheet that has my new gears. I'll try to get the others put in the next few days.

Needless to say - I'm pretty excited to get these. Folklore on Nasioc says these should hold upwards of 300 chp without trouble and will be great for when I get around to that. Until then though, they'll be great for daily/highway driving and for on the track.

Can't wait to get the tranny in - thanks Matt!!

[music] who loves short ratios? we love short ratios! [/music]

AWD_addict · Post by **AWD_addict** » Thu Mar 05, 2009 5:02 am

That looks like a good spread of ratios, should keep you in the powerband nicely!

GodSquadMandrake · Post by **GodSquadMandrake** » Thu Mar 05, 2009 7:18 am

Matt Monson wrote:
skid542 wrote:
Over on NASIOC guys are calling these LGT gears. I consider that a bit of a misnomer. While the 2004 LGT was the first time we here in the states saw these ratios used, they were originally introduced in the V5 STi and continued through the v6 STi and Prodrive P1, but with a super short ring and pinion of 4.44. In fact, Rallispec has been selling these ratios for years as just that, STi stree ratios, at a slightly lower price than their RA gears. They are also the same ratios found in my 2008 WRX, except in that car we get a shorter 0.78 5th gear.

The final drive of 4.44 is in the differentials and not the actual gear set itself. Did you swap over your differentials to 4.44 too? I've been wanting to figure out how to do that because it seems like it would be great for the low speed high acceleration of rally, autocross, and rallycross. Where did you source the differentials or did you just change the ring and pinion? How much does it cost?

It seems like most of the guys on Nasioc are concerned with getting a stronger gearset rather than a better gear ratio. It doesn't seem like there is any good answer though. You're going to end up spending $3-6,000 depending on whether you just get a 6MT, Mfactory gears, or PPG gears. I know the RA gears are an option and you can optionally have them crio treated and shot peened but even if you do all that the RA gears are only like %25 stronger and it just means they'll break less often - they'll still break. I wish there was an OEM option to get an off the shelf transmission that was durable but there is no good answer for less than $5,000.

I just have a hard time spending $5,000 on the transmission alone because that's more than my car and my engine cost. The transmission seems like the biggest weak point though.

skid542 · Post by **skid542** » Thu Mar 05, 2009 2:07 pm

The final drive of my box is 3.90. The ratio chart I posted reflects this. The ratios between gears is a function of the gears themselves, the final drive differentials are just a multiplier. I have these ratios and a 3.90 final drive because the 1-2 and 3-4 mainshafts of the WRX tranny have been replaced with brand new LGT/STi 1-2 and 3-4 shafts.

These are not RA gears. The STi/LGT gears are different.

If you can complete a full 6spd swap for $3,000 you're not getting a new tranny and will likely have issues down the road due to the fact it was used and sold for as cheap as it was. Not saying it can't be done, just not very likely.

I am getting an almost brand new gearbox that will last me another 40k easily before I have any troubles with it (assuming I treat it right, which I will).

I also did not spend $5,000 for this gearbox.

And there's a point where if you want play - you have to pay. Whether that's the tranny, motor, suspension, or brakes.

Matt Monson · Post by **Matt Monson** » Thu Mar 05, 2009 3:38 pm

GodSquadMandrake wrote:
The final drive of 4.44 is in the differentials and not the actual gear set itself. Did you swap over your differentials to 4.44 too? I've been wanting to figure out how to do that because it seems like it would be great for the low speed high acceleration of rally, autocross, and rallycross. Where did you source the differentials or did you just change the ring and pinion? How much does it cost?

Just a correction and clarification of terminology. 4.44 final drive ratios are NOT in the differentials. They are in the ring and pinions. The differential (and what type of open or limited slip) that you choose is independent of the final drive, which is mandated by the ring and pinions.

There are 2 ring and pinions in an AWD transmission. There's one in the front inside the transmission case and there's a second pair in the rear end coupled to the rear differential.

To convert to a 4.44 with new parts is pretty expensive. It requires replacing both, which puts you in the ballpark of a set of gears. The cheap way to move over to 4.44 is to find a Forester XT or Outback XT transmission and rear differential and install them. The only downside of that approach is the Outback doesn't use a rear LSD. The Forester, however does. You can also try to find a JDM transmission (which I have available, BTW. I just don't have a 4.44 rear end right now) and go that route.

skid542 · Post by **skid542** » Thu Mar 05, 2009 3:44 pm

Thanks Matt for the clarification on the differentials vs. ring and pinions. I had a feeling my terminology was still a bit incorrect.

Matt Monson · Post by **Matt Monson** » Thu Mar 05, 2009 4:04 pm

skid542 wrote:The final drive of my box is 3.90. The ratio chart I posted reflects this. The ratios between gears is a function of the gears themselves, the final drive differentials are just a multiplier. I have these ratios and a 3.90 final drive because the 1-2 and 3-4 mainshafts of the WRX tranny have been replaced with brand new LGT/STi 1-2 and 3-4 shafts.

Lee,
I don't think your terminology is vague. This explanation is very clear and succinct.

93forestpearl · Post by **93forestpearl** » Thu Mar 05, 2009 4:12 pm

skid542 wrote:
If you can complete a full 6spd swap for $3,000 you're not getting a new tranny and will likely have issues down the road due to the fact it was used and sold for as cheap as it was. Not saying it can't be done, just not very likely.

+1. I sourced mine with only 8k on it, but damn, those were a rough 8k. I'm not worried about breaking it, but it could use a set of syncros. She doesn't like a hard 1-2 not matter what oil I use...

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I bought a Modena front LSD

I bought a Modena front LSD