Notices
GT4/Spyder Discussions about the 981 GT4/Spyder
Sponsored by:
Sponsored by: APR

GT4 final drive discussion

Thread Tools
 
Search this Thread
 
Old 10-05-2015, 01:10 AM
  #61  
user1029
Drifting
 
user1029's Avatar
 
Join Date: Feb 2015
Posts: 3,181
Received 564 Likes on 277 Posts
Default

Originally Posted by s2ktaxi
if the car weren't already so low to the ground, we could just use smaller wheels/tires with a 15% smaller diameter
Not that it hasn't stopped anyone
Old 10-06-2015, 01:43 PM
  #62  
GTgears
Nordschleife Master
 
GTgears's Avatar
 
Join Date: Oct 2009
Location: Loveland, CO
Posts: 5,163
Received 123 Likes on 86 Posts
Default

Originally Posted by CAlexio
Is it possible that this becomes such a commonly needed fix, that opening the gearbox for this particular car becomes the "de rigeur" modification everyone does? If enough people want to shorten the final drive, maybe gtgears et al will finally have a good business case on their hands.
I've been meaning to come back to this thread for a few days but am always on my phone when I pop in to RL.

For me, at least, there will never be a R&P option. As I have stated elsewhere I am out of the R&P business completely. It's not just a Cayman thing. It's that it does not make a good business case, to use your terms. I ran the numbers this morning. I sold 15 GT3 R/Ps in 2014. I would say half of those went into Cup Cars. I'm not going to argue against Pete's assertion that a lot of guys are buying OEM units for their cars because it's not wholly relevant. Even if Porche and PMNA sells twice as many as I do, it's not a big enough market to make it worth my while. It was a 5 year experiment that I have deemed not successful enough to keep it part of my product assortment.

I checked gear sales for the same period. I sold enough GT3 gears to regear almost 50 cars. Based purely on my memory of my conversations with the shops that I sell to (I do not sell retail even though I often consult with the end users) I would say that 2/3 or more of the GT3 gears were for DE guys and not racecars. My lower numbers for 6th gear sales support this as many DE guys will reuse the stock 5th in 6th position to save some money. I sell about 25% fewer 6th gears than other positions.

I always tell people that I am a motorsports manufacturer and I base my business decisions off of what I can sell for use in racecars. That has changed somewhat in recent years with a more affluent customer base of DE guys. 911SC and 3.2 Carrera DE guys still don't buy gears. GT3 guys do quite often.

I think there is some truth to Kman's post about this car being different. It's more that I think the owners are different. You guys are GT3 like in your spending patterns on your track toys. It's no accident that I've never made 997 Carrera gears. Not only was there never a race series that allowed us to change ratios, but Carrera owners are NOT GT3 owners. GT3 owners have benefitted from the fact that their cars use Cup Car parts in their gearboxes. We've been making Cup gears for 15 years and GT3 street cars have only been around for 10.

And because the car owner's base is unique, I have commited to production of these parts for it. I don't expect them to ever pay my bills. I've sold 6 complete sets of Cayman gears in the year that they have been on the market. Only 2 of those sets are in DE cars, but that's still 1/3 of the "market". They will never ever sell 40 or 50 gearboxes worth of gears per year even though I sell 80-100 Cayman LSDs per year. The gearbox does not have to be opened up to install an LSD. And the same 1-2 seconds per lap that $4500 worth of gears will get you can be had in a $2500 LSD. So the LSD always wins the limited mod $$$ math.

My last comment would be regarding R/P versus gears with respect to one of Pete's comments. The final drives for 944 were abour $1500. It was 1/3 of the cost of gears and there was only ever 1 single gearset option for the 944. Not a good comp. For a GT3, gears vs ring and pinion are about a zero sum game. Installing a ring and pinion takes approx 5 more hours than doing gears. The gears cost $500 more in parts but have less labor. The idea that a ring and pinion is an easier sell has not historically been the case. If one reads around here on RL, you will see conversations about gears versus r/p. The conversation always turns to rpms drops. Gears fix the poor spacing between the gears. The r/p only moves the power around to somewhere else with the same gaps on shifts. A lot of GT3 guys who do ring and pinion swaps do it because they destroyed their stock r/p and had to buy a new one. It's not because it was the best mod but because when you are about to spend $3000 to replace your ring and pinion, buying a 3.44 from the dealership and buying a 4.00 from PMNA or GT, if you are a track guy you buy the 4.00 every single time. Gears wear out less frequently than r/ps.
Old 10-06-2015, 01:53 PM
  #63  
GTgears
Nordschleife Master
 
GTgears's Avatar
 
Join Date: Oct 2009
Location: Loveland, CO
Posts: 5,163
Received 123 Likes on 86 Posts
Default

Wanted to make a separate post so it was easier for guys to extract. Rshanholtz is running our shortest gear kit in his car.

1.650 3rd
1.333 4th
1.100 5th
0.962 6th

You guys can plug that into your charts if you want to see how it stacks up. I don't really think the comment that 3rd is so close to 2nd now that you don't need it is as accurate as saying that for many road courses you don't need 2nd when you have properly spaced gears. 1.95 to 1.65 isn't super tight. It's close but not super close.
Old 10-06-2015, 02:42 PM
  #64  
Petevb
Rennlist Member
 
Petevb's Avatar
 
Join Date: Oct 2003
Posts: 3,728
Received 705 Likes on 282 Posts
Default

Originally Posted by GTgears
The idea that a ring and pinion is an easier sell has not historically been the case.
My impression it that it depends on the application and availability.

For race cars I agree gears usually make more sense. For a street/ track car the reduced gear noise of a hypoid R&P is attractive vs straight cut individual gears, as is the reduction of the total stack rather than the top end focus usually seen with gears.

I've got (and have had) both gears and a ring and pinions in my cars, and for the GT4 for dual use a R&P remains very attractive even if the price were similar... sound like it's a moot point for now, however.

Anyway. Below is how the short gears above look. Big track focused:

Old 10-06-2015, 02:54 PM
  #65  
GTgears
Nordschleife Master
 
GTgears's Avatar
 
Join Date: Oct 2009
Location: Loveland, CO
Posts: 5,163
Received 123 Likes on 86 Posts
Default

Originally Posted by Petevb
My impression it that it depends on the application and availability.

For race cars I agree gears usually make more sense. For a street/ track car the reduced gear noise of a hypoid R&P is attractive vs straight cut individual gears, as is the reduction of the total stack rather than the top end focus usually seen with gears.
I don't really think you can make the sort of statment in the 2nd paragraph and it's because of the first paragraph's truth. The ring and pinion gives you 1 single top end option, which is generally 12-15% slower than stock.

On the GT3, for example, we manufacture 3 dozen different 6th gear ratios. The only "top end" focus there is is matching the ratio choice to what track you run and giving yourself exactly just enough legs to complete your fastest straight away without running out of gear.

Or, for a DE guy, he doesn't have to change 6th gear at all. He can keep his stock 6th for crusing the highway quietly too and from the track. 2 of our Cayman kits are exactly this, with 3-4-5 changed because if it's not a racecar, why stack them so closely together when you still want to drive the car on the street.

Yes, our gears make more noise than stock. But they are NOT straight cut. That's not why make noise. Most aftermarket r/p sets make noise too. Ask anyone with a 996 Carrera who bought one of the Albins 4.00s. Only OEM ring and pinions will be OEM quiet. Unless Porsche themselves makes one for the Cayman, expect it to make noise. Motorsports parts are manufactured with strength in mind and it's not being palloid or even helical that automaticallly it run quietly.
Old 10-06-2015, 03:23 PM
  #66  
Petevb
Rennlist Member
 
Petevb's Avatar
 
Join Date: Oct 2003
Posts: 3,728
Received 705 Likes on 282 Posts
Default

I thought you'd mentioned that the taller Audi diesel ratios fit the box, and hence could then provide quiet taller 6th options? Or was that on another gearbox?

On one of my boxes I did have the luxury of both a shorter factory R&P and taller factory gears from other models, which seems ideal. Currently it looks like a null set for the GT4 what I suspect is a street/ track car ideal, which would be quiet gears and a short 1-5. I certainly agree a noisy of short 6th would be something to be avoided on a street car.
Old 10-06-2015, 03:57 PM
  #67  
GTgears
Nordschleife Master
 
GTgears's Avatar
 
Join Date: Oct 2009
Location: Loveland, CO
Posts: 5,163
Received 123 Likes on 86 Posts
Default

Originally Posted by Petevb
I thought you'd mentioned that the taller Audi diesel ratios fit the box, and hence could then provide quiet taller 6th options? Or was that on another gearbox?

On one of my boxes I did have the luxury of both a shorter factory R&P and taller factory gears from other models, which seems ideal. Currently it looks like a null set for the GT4 what I suspect is a street/ track car ideal, which would be quiet gears and a short 1-5. I certainly agree a noisy of short 6th would be something to be avoided on a street car.
I don't sell "their" stuff. But in all seriousness, the TDI 5th and 6th gears are uber tall. Like .60 kind of stuff meant for a car to cruise the Autobahn at 90mph at 2800rpm. There's not really a midway option if you came up with a ring and pinion. Only guy who would ever want those Audi gears would be a guy with a boosted Cayman running the Texas Mile trying to break into the 200mph club.

BTW, we can alter toothcounts and tooth profiles to make gears run quietly, however it is at the expense of strength. We would never do it on our race gears. But we've done custom one offs for 915 guys here and there that just had to have factory quiet gears on their 73 RS. For some guys, cost is irrelevant and paying for a custom one off production. Most guys however buy off the shelf "suits" for considerably less. The mainshaft 1-2 is no different.
Old 10-06-2015, 04:25 PM
  #68  
sunnyr
Three Wheelin'
 
sunnyr's Avatar
 
Join Date: Mar 2011
Location: Bay Area, CA
Posts: 1,375
Received 137 Likes on 75 Posts
Default

Maybe this was already answered - but doesn't the base Cayman gear box have shorter ratios?



Will that gearbox work on GT4? or can that unit not handle the torque of the 3.8? Other issues with using it?
Old 10-06-2015, 04:29 PM
  #69  
GTgears
Nordschleife Master
 
GTgears's Avatar
 
Join Date: Oct 2009
Location: Loveland, CO
Posts: 5,163
Received 123 Likes on 86 Posts
Default

Those are PDK ratios in parentheses. But yes, the base model gearbox get a "better" 2nd and slightly improved 3&4. I thin anyone who bought a gearbox to rebuild with short 3-6 would buy the base gearbox for the improved 2nd. No, it isn't weaker. Same basic architecture, minus the cooler. I think they are largely using up 987.2S castings to get through their stock of inventory. While I make things 10 or 20 at a time they make them 1000 at a time.
Old 10-06-2015, 04:40 PM
  #70  
sunnyr
Three Wheelin'
 
sunnyr's Avatar
 
Join Date: Mar 2011
Location: Bay Area, CA
Posts: 1,375
Received 137 Likes on 75 Posts
Default

Yes, should have clarified - the ones in parentheses are for PDK. Ignoring those, it still looks like everything but the 4th is shorter in the base cayman gear box.

Original doc I got the figures from - http://press.porsche.com/vehicles/20...ifications.pdf
Old 10-06-2015, 04:49 PM
  #71  
GTgears
Nordschleife Master
 
GTgears's Avatar
 
Join Date: Oct 2009
Location: Loveland, CO
Posts: 5,163
Received 123 Likes on 86 Posts
Default

Woops. I was only looking at the right side. Somehow I completely missed the non-S ratios on the left of your chart...
Old 10-06-2015, 06:09 PM
  #72  
Ochocoronas
Pro
 
Ochocoronas's Avatar
 
Join Date: Aug 2015
Posts: 578
Likes: 0
Received 1 Like on 1 Post
Default

So who's going to be the 1st person to crack open their transmission ? What about swapping out to the base Cayman transmission? When someone does let me know how it works. I am in the camp with GT Gears... not many people are going to follow through on doing anything when it comes down to it. IMO its not that bad and I could think of a ton of things I would rather spend that money on.
Old 10-06-2015, 06:39 PM
  #73  
Petevb
Rennlist Member
 
Petevb's Avatar
 
Join Date: Oct 2003
Posts: 3,728
Received 705 Likes on 282 Posts
Default

Originally Posted by sunnyr
Yes, should have clarified - the ones in parentheses are for PDK. Ignoring those, it still looks like everything but the 4th is shorter in the base cayman gear box.
I posted a comparison of those ratios vs stock on page 3, repeated here:

Old 10-06-2015, 06:54 PM
  #74  
sunnyr
Three Wheelin'
 
sunnyr's Avatar
 
Join Date: Mar 2011
Location: Bay Area, CA
Posts: 1,375
Received 137 Likes on 75 Posts
Default

^Thanks Pete. And the speeds -

Gear - Stock GT4, Base Cayman
1st Gear - 48.47 mph, 43.72 mph
2nd Gear - 82.28 mph, 78.26 mph
3rd Gear - 113.79 mph, 109.89 mph
4th Gear - 141.98 mph, 141.98 mph
5th Gear - 168.88 mph, 165.4 mph
6th Gear - 198.07 mph, 191 mph

Don't seem to much better.
Old 10-06-2015, 07:04 PM
  #75  
GTgears
Nordschleife Master
 
GTgears's Avatar
 
Join Date: Oct 2009
Location: Loveland, CO
Posts: 5,163
Received 123 Likes on 86 Posts
Default

I'd have to double check but I think that 5th and 6th are the 987.2 6spd ratios that Interseries guys used to put in their cars as cheater gears for just a little extra oomph. It's not much, but in 2013 at the 24 Hours of Daytona is made a difference of about 1 second a lap. When you run 30 laps an hour over 24 hours, a second is minutes by race end.


Quick Reply: GT4 final drive discussion



All times are GMT -3. The time now is 06:14 AM.