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Discussion Starter · #1 ·
Hello,
So enough people are racing these cars that the gearboxes are starting to come apart with regularity. That's the point at which, as a business, it becomes a viable consideration for us to offer alternative gear ratios for your cars. Given that, I want your input.

Historically, for the G50 family of gearboxes, which includes the GT3's and Twin Turbos, we've made pretty much ever ratio under the sun. The demand was there because it's line of gearboxes that spans over 20 years of production and counting. There's so many different applications and configuration for those things that it was warranted.

With the Cayman S/Boxster S we are going to start this process conservatively and probably just make a couple of "kits". By a kit I mean 3-4 ratios that work well together that are going to offer people the choice to set up for different tracks (short boxes and long boxes) or have an all arounder box that's just better than stock. We'll also probably do a couple of mainshaft options so that you can consider changing 1st and 2nd as well.

So, I am looking for feedback from the guys who are racing. Tell me what you are experiencing out there on the track. You can be general or you can be specific. If you've got a problem in your car exiting turn 11 at Sears Point tell me about it. Tell me about speeds, tell me about RPMs. In short, talk to me about where you run and about where your gearbox currently leaves you flat. Tell me if you run out of rpm and need another 500 at the end of a straight, or where you're just off the power coming out of a corner and neither gear choice you can make feels right.

From this information, I will be better equipped to come up with some alternative ratios and gearcharts that will suit a variety of applications and uses so that we can offer you the best lap times and performance that your car can offer. PowerhausII used to claim that regearing your car is like picking up 30bhp. I subscribe to that line of thinking, and with new gear options, I promise that we'll help make you faster.

Also, please help me learn more about your gearboxes. How many different variants of them currently exist? What are the factory ratio changes or final drive changes from year to year. A lot of this information isn't easy to find and having a solid starting point with good details will make it easier to plug in other ratios where I see holes in the current stack.

Thanks for your time and input.
 

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Hello,
So enough people are racing these cars that the gearboxes are starting to come apart with regularity. That's the point at which, as a business, it becomes a viable consideration for us to offer alternative gear ratios for your cars. Given that, I want your input.

Historically, for the G50 family of gearboxes, which includes the GT3's and Twin Turbos, we've made pretty much ever ratio under the sun. The demand was there because it's line of gearboxes that spans over 20 years of production and counting. There's so many different applications and configuration for those things that it was warranted.

With the Cayman S/Boxster S we are going to start this process conservatively and probably just make a couple of "kits". By a kit I mean 3-4 ratios that work well together that are going to offer people the choice to set up for different tracks (short boxes and long boxes) or have an all arounder box that's just better than stock. We'll also probably do a couple of mainshaft options so that you can consider changing 1st and 2nd as well.

So, I am looking for feedback from the guys who are racing. Tell me what you are experiencing out there on the track. You can be general or you can be specific. If you've got a problem in your car exiting turn 11 at Sears Point tell me about it. Tell me about speeds, tell me about RPMs. In short, talk to me about where you run and about where your gearbox currently leaves you flat. Tell me if you run out of rpm and need another 500 at the end of a straight, or where you're just off the power coming out of a corner and neither gear choice you can make feels right.

From this information, I will be better equipped to come up with some alternative ratios and gearcharts that will suit a variety of applications and uses so that we can offer you the best lap times and performance that your car can offer. PowerhausII used to claim that regearing your car is like picking up 30bhp. I subscribe to that line of thinking, and with new gear options, I promise that we'll help make you faster.

Also, please help me learn more about your gearboxes. How many different variants of them currently exist? What are the factory ratio changes or final drive changes from year to year. A lot of this information isn't easy to find and having a solid starting point with good details will make it easier to plug in other ratios where I see holes in the current stack.

Thanks for your time and input.
That would be awesome !!! (to have custom gear ratios). A simple solution would be just to have a 8-13% (per my calcualtions and readout of telemetry of most tracks in the East - Daytona through Road America). That would make the car SO MUCH faster. Or alternatively just close the gap between 2nd and 3rd (too long for only 300hp), and bring in down (shorter) 4th and 5th accordingly.

Cant be done in PCA stock classes, but will make the car the definitive killer in NASA (no rules apply) GTS classes. I have a spare gearbox (with one of your diffs and all) to use as backup or to have as my NASA only setup, so will be more than willing to test it for you.
 

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My only comment is when I put on my track tyres which have a slightly smaller diameter than my road tyres, the acceleration is much better in all gears. I like all the gear ratios between gears with this setup. It would be nice to have a similar overall ratio % change all the time. I change to Rear to 295/30R18 from stock. Whatever that works out to be % wise.
 

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Discussion Starter · #4 ·
This brings up a great point. What are the most common size tires being used in a racing application on this car? As was mentioned, tire size can have a huge impact. A couple of years ago, the spec size on the vintage 911's changed by about 1/2" in total diameter. Suddenly everyone was having to change the gear ing on their 901 gearboxes to match the new tire requirements. Even as little as half an inch makes a difference.

It is too bad that since Porsche has never raced the car themselves that there's no homologation ratios like there are for the GT3. Often the PCA follows the homologation rules for what they allow with cars. But I'm not so concerned with that since there are a lot of different sanctioning bodies and classes in both amateur and professional racing. My goal here is to help get these cars on the podium wherever they race. And in many instances, rules can be rewritten over time to concur with the racers' desires. That's what happened with our LSD in Interseries.
 

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Cayman The Destroyer!
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Unless you are drag racing, just want to have 0-60 bragging rights or going to pull some stumps a shorted first gear is a waste. But that's just my view because I never give into the temptation of "red light" drags.

I'd like to see a lower ratio second gear. There are some turns I run into that are just a little to fast to make a down shift to second but are on the low end of the power band with third. 275/ 35 or 40 rear tires
 

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Unless you are drag racing, just want to have 0-60 bragging rights or going to pull some stumps a shorted first gear is a waste. But that's just my view because I never give into the temptation of "red light" drags.

I'd like to see a lower ratio second gear. There are some turns I run into that are just a little to fast to make a down shift to second but are on the low end of the power band with third. 275/ 35 or 40 rear tires
BTW my request wasn't to create a drag-race car, only to put the Cayman at least on par with the 911 since the Cayman and Boxster get artificially held back by the gear ratios that Porsche has provided.
 

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Cayman The Destroyer!
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I understand your point but It's not something I see as being a big deal. On the street a few 10ths to 60 really doesn't mean much to me. Don't forget that GT'3s have more revs to work with and need to get up in the power band faster.
 

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Discussion Starter · #9 ·
So,
I've started running some numbers and chewing on this a bit more and need some input. What kind of top speeds are you guys hitting on the long tracks that you run? Can you hit 140mph? What about 150mph?

Looking at the splits, it's not really a badly stacked gearbox, except 5 to 6th. that's not to say that we can't make improvements though. However, I imagine making that shift out of 5th at 135mph+/- into 6th feels like it just hit a wall and isn't going anywhere. But do you guys have enough power to currently even make it into 6th anywhere that you run?

As far as the whole 0-60 conversation? I don't think there's a single gearbox that we make a 1st gear for that is shorter than stock other than old 930 4spd. Everything is taller in 1st with second being either up or down according to application. When we do a mainshaft for this box, it will probably just be one ratio and likely something like the 3.1 you see in Cup Cars. It's a good pit gear that you don't have to rev to the moon to get off the line.
 

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Discussion Starter · #11 ·
Just as an FYI, I am using a 6500rpm shift point and 275/40/18 tires for my modelling. When I start to put up the ratios I am thinking about and mph and rpm drop numbers to go with them, there will be discrepancies of several miles per hour and a few hundred rpms for different set ups. Just going down to the 275/35/18's some people run changes the top of 4th gear by 5mph because it's a full 1" smaller in diameter than the 40's.
 

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Cayman The Destroyer!
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I think 7000 is a more realistic shift point red line is 7200. Top speed for me is 141 in 5th at vir is the highest speed I've seen
 

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Discussion Starter · #13 ·
The shift point is a balancing act. The problem with moving it too high is it ignores the early CS's that make peak HP at 6250 versus the late ones that make it at 7000. Something like this needs to work for the least common denominator, and won't really penalize those who can shift higher. But overgearing it for the later more powerful cars and then putting the stack in a 2006 CS would leave them flat on their face in the higher gears.
 

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I've not hit above 140 on any track yet. With a turbo, it would probably bump me to 150 or so. I can't imagine getting much above that on the tracks I've been on. This is a mod that would interest me, depending on the specifics. How much would you expect it to cost?
 

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I hit 140 on most tracks being very close to redline in 5th at the fastest straight of some, but only use 6th gear at Daytona.

From my analysis of the Telemetry, I dont think there's a need for a much shorter 2nd gear (5% shorter max). The slowest corners at any track are 40-45mph apex and the car is at peak torque in 2nd at that speed.

Main benefit will come from a much shorter/closer gear steps between 2-3-4-5 (and 6th too b/c if 5th is shorter you will be making that change more often).

See below the video with Telemetry of my fastest laps at some tracks, so you can see the shiftpoints, corner speeds and straight speeds:

Road Atlanta:
Road Atlanta PCA Race 2010 - H Stock Cayman S - 1:36.1 on Vimeo

Sebring:
Sebring PCA Race 2010 - H Stock Record Cayman S on Vimeo

Daytona:
Daytona PCA Enduro Race 2009, I Prepared Cayman S on Vimeo

Road America:
Road America PCA Race Qualifying - H Stock Cayman S on Vimeo

Mosport:
Mosport 2009 PCA Club Race - H Stock Cayman S Qualifying on Vimeo

VIR:
VIR PCA H Stock Cayman S - 2:09 on Vimeo

Watkins Glen
Porsche Cayman S - Watkins Glen on Vimeo
 

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Just as an FYI, I am using a 6500rpm shift point and 275/40/18 tires for my modelling. When I start to put up the ratios I am thinking about and mph and rpm drop numbers to go with them, there will be discrepancies of several miles per hour and a few hundred rpms for different set ups. Just going down to the 275/35/18's some people run changes the top of 4th gear by 5mph because it's a full 1" smaller in diameter than the 40's.
If you look at the torque curve (my car is an 06 with old non-DFI engine), even with the current broad gear spacing of the stock gearbox the optimal changing point is ALWAYS redline. Torque at wheels is ALWAYS higher in the lower gear. I would model with that.
 

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Discussion Starter · #17 ·
If you look at the torque curve (my car is an 06 with old non-DFI engine), even with the current broad gear spacing of the stock gearbox the optimal changing point is ALWAYS redline.
I have looked at the dynosheets and the torque curve on these engines. I think it's BECAUSE of the current broad gear spacing that you have to shift at 7000+. If you didn't, you wouldn't be hitting the sweet spot on the powerband. That's the problem with most factory gear stacks.

Thank you for the videos, they are very useful. They give me a good idea of where to go with this. The way it's stacking up, it looks like there's going to end up being two different stacks, with one of them having an optional 6th gear.

The first stack will be the "tall" stack. It will have alternative 3rd, 4th, and 5th gears. It will keep the stock 6th gear for guys who still drive their car on the highway and to the track. Top of 5th will be a tick over 130mph at 6500rpm. That's just over 140mph if you run it up to 7000. This will have the option of getting a 6th gear that will take you to 160mph in 6th at 7000rpm.

I don't think that the stock power levels cannot push that 6th gear to redline in a reasonable distance. But the way I see tuning on these cars going over time, it will be useful. A turbo car can push that gear. And as all motor builds happen and more aggressive cams are introduced and the redline gets pushed another 500-1000rpms with retuning that will be a useable 6th gear. And just so we're clear on this, while I call it the "tall" stack, it's still shorter than stock.

Also optional on that stack is going to be the mainshaft kit. This will NOT involve a shorter than stock 2nd gear. 2nd gear will be taller, making it even closer to 3rd gear than the stock 2nd gear. 1st gear will also be taller. There are a couple of reasons why someone might want to consider the mainshaft kit. One of them would be if they were an auto-crosser. The taller 2nd gear will be an advantage there. And it's not so much taller than stock that you couldn't keep the stock 3rd gear in there.

The other reason for a road racer is that we're starting to see the stock factory mainshafts get eaten up in racing. But it's not how you would think. It's not the 1st or 2nd gears and their dogs (which are a standard wear issue) so much as the splining on the shaft itself. The area where the 3rd and 4th gear fixed gears, and the 3/4 slider slip onto the mainshaft are seeing significant wear and I suspect that on cars that are raced, mainshaft replacements are going to start to become a common service on these boxes on their 2nd, or 3rd refresh. So figure 2-3 seasons of racing and it's going to need a mainshaft. So, my logic is, if they are going to be replaced, we should make a better one available.

The other stack will be the "short" stack. This will be only offered as a 3,4,5, and 6 kit. Top of 6th gear at 6500rpm will be 145mph. Pushing it to 7000 will take you up to 155mph. The stock, or mostly stock, engines can push this with the right drops. This gives you a safe margin for most places that people run. We NEVER push the top speed in the top gear all the way to redline. Daytona is a good example of where we've seen this play out time and time again. Guys go there and try to run their all around gearbox. What happens is they find themselves right up against redline in their top gear for a good 30 seconds or so. And what happens? The engine eats a rod bearing and it costs you a rebuilt motor. With this stack, you can safely push your car to 145-150mph as a peak speed at the end of the straight, but wouldn't be for anything sustained at those speeds. If you're someone who runs Daytona then you'll want to look at the other stack.

Above someone asked about cost. Historically, our GT3 gears have run $925 and our 915 gears run $750. I expect these gears to fall somewhere in between there. The mainshaft, if we build it with two integral gears, will probably be around $2500. If we do it with a swappable second gear, it's more expensive and will be closer to $3000.

I'll post up the various ratios we're considering for review and input. I know some of you will want to plug them into charts and run some numbers. I want you to be able to do that before anything gets set in stone so that we can get your feedback and incorporate it into what the final product becomes.
 

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Matt,

Can you summarize the options you are planning to offer in a table that compares the ratios to the OEM ratios? Therefore we can use the info to make a decision on which suits us bests for the tracks we run.
I think my spare box is still there at GT (? fixing 2nd gear that never worked quite right after the rebuild), so it would be awesome to get it with the new gears
 

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Discussion Starter · #19 ·
Hello,
Sorry I've been out of the loop for a little while here. I had a family emergency in CA the middle of last week and shut the shop and left town. Also, for some strange reason I stopped getting updates when a new reply is posted.

First off, I want to clarify what I suspect is a point of confusion. I know I've seen it mentioned on other boards. I have ZERO affiliation with Gbox, where I suspect your gearbox is being serviced. Somewhere someone started a patently false rumour that they were the ones that bought Guard Transmission. There's no truth to it. I own Guard Transmission with Paul Guard as my silent minority surf/snow bum partner. If you want to see how things stand with Gbox and GT just go over to Rennlist and hit the Cup Car forum in the motorsports area. Gbox's salesman posted one of his "Got to get a Giken" infomercials and was bad mouthing the GT LSDs enough that Paul Guard himself stepped in and challenged his false claims. Paul poured 20 years of his heart and soul into these products and wasn't going to see his product, that he developed, dragged through the mud by a salesman with less than 2 years experience in the business who was talking out his arse.

However, don't get me wrong. Stan, the owner at Gbox continues to be a friend of mine, and I consider him one of the 5 best Porsche gearbox mechanics in North America. Your gearbox will get nothing but the best service at his hands. However, with his salesman taking the approach he did, he pretty mich single handedly ended the business relationship between the two shops. He made a choice. He chose to sell Giken LSDs instead of Guard LSDs. I personally think it was a big mistake. Giken makes LSDs for 2 p-car applications. We make them for 15. He could have sold both products side by side and covered everything out there. But instead he pitted the two brands against each other and picked to sell just one. Sorry, it's a sore subject and puts a bug up my arse everytime someone mistakenly thinks they own my business.
/rant

I will get you the list of ratios I am considering with some other data points by the end of the weekend. I'm currently digging out of the customers I was unable to service while I was tending to my sick brother in the hospital. Be paitent with me for a couple of days and I'll give you information.
 

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I'm interested though I'm curious as to ballpark cost figures. It's not like an S2000 or a Mustang where we can swap the rear end/final gear and call it a day...
 
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