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Gear ratios of 997 GT3

 
Old 02-15-2007, 09:55 PM
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MM3.9GT3
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Default Gear ratios of 997 GT3

Why is the 997 GT3 geared so "long"? I calculated the maximum speed in each gear, and got the following numbers (approximate).

1st = 49 MPH
2nd = 82 MPH
3rd = 113 MPH
4th = 144 MPH
5th = 183 MPH
6th = Top speed

Has anyone changed the gearing (axle ratio)? I would think that acceleration would be noticeably improved.
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Old 02-15-2007, 10:02 PM
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I changed the axle ratio on my 996 GT3 from 3.44:1 to 4.00:1. Acceleration noticeable improved? Yes, a lot.

The nice thing about the 996/997 GT3 transmission is that you can change gears, and R&P (axle ratio) to your personal preference.
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Old 02-15-2007, 11:01 PM
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Originally Posted by NJ-GT
The nice thing about the 996/997 GT3 transmission is that you can change gears, and R&P (axle ratio) to your personal preference.
Yes, that is a nice thing (and much bigger improvement than changing just R&P), but doesn't it cost an absolute fortune to do so?
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Old 02-15-2007, 11:05 PM
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I am assuming that you got the 4.00:1 R&P from a performance shop. Can you please give me an approximate price, and point me to a source/website?

Thanks for your help.
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Old 02-16-2007, 03:30 AM
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One source: Mr. Brian Copans at BMC&G in Ohio.

Cost, including shipping, around $3,000 for the forged R&P from the 997 RSR.

Re-gearing or changing the R&P is cheap. A set of wheels is about the same price, same as a cage, don't even mention PCCB.

Bottom line is that we get a transmission that can be tailored to personal preferences, at affordable cost.

The LSD and Flywheel can be upgraded on that same trip.
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Old 02-16-2007, 11:55 AM
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Originally Posted by NJ-GT
One source: Mr. Brian Copans at BMC&G in Ohio.

Cost, including shipping, around $3,000 for the forged R&P from the 997 RSR.

Re-gearing or changing the R&P is cheap. A set of wheels is about the same price, same as a cage, don't even mention PCCB.

Bottom line is that we get a transmission that can be tailored to personal preferences, at affordable cost.

The LSD and Flywheel can be upgraded on that same trip.
Re-gearing is changing the gear stack (the actual ratios of each or some of each of the 6 gears). This is where the big benefit is (closer spacing gives much better track performance and is a much bigger deal than changing R&P. I'd love to see a price for changing 4 ratios (3rd-6th) or even 5 ratios (2nd - 6th) - it won't be cheap...
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Old 02-16-2007, 12:05 PM
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Not only is it not cheap but reliabilty becomes an issue as well. But nothing beats a well designed gear ratio for the track!
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Old 02-17-2007, 12:33 AM
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The 996 GT3 and 997 GT3 have very good gearing from 3rd to 6th. Reducing the R&P allows the car to be driven from 3rd to 6th at every track.

Indeed, on a comparison chart with the stock R&P, new 3rd, 4th, 5th, and using the stock 5th into 6th, the speeds in gears are about the same as the stock gears with Cup R&P.

The optimum solution is to re-gear 1st to 6th with a custom R&P, but it's expensive. Re-gearing 3rd,4th and 5th costs about the same as a forged short R&P.
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Old 02-17-2007, 12:38 AM
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Originally Posted by NJ-GT
The optimum solution is to re-gear 1st to 6th with a custom R&P, but it's expensive.
If you re-gear 1st through 6th, why would you need to change the R&P? Is it just for the durability of the forged unit? Otherwise, given enough choices of gears, it shouldn't be necessary...
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Old 02-17-2007, 01:20 AM
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Porsche has very limited gear rates available for this transmission, so it's necessary to use the 4.00 R&P, a long first (3.15) and the proper spacing up to sixth. The 997 GT3 Cup has the closest thing to perfect gearing for these car.

With the stock 3.44 R&P, the shortest 2nd available is still too long (over 80 mph). Only the 5th and 6th gears are compatible, 3rd and 4th are unique, and 1st and 2nd are integrated into the shaft (fixed). The GT3 Cup shaft has only a fixed 1st (3.15) but that's too long for the 3.44 R&P.
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Old 02-17-2007, 01:49 AM
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Does the street GT3 have a G96/91 trans ? I have a GT3 RS 2001 Trans in the shop right now the R& P got loose and backed off and started to rub on the case cover. The Mechanic said he cant get a short track R&P from Porsche only a Daytona R&P which is really tall top speed over 200mph, is there an after market short track R&P?? thanks Ferd
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Old 02-17-2007, 10:39 AM
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The street 996 GT3 and GT3 RS use the G96.96, two R&P are available from Porsche, the 31:9 and 32:8. The street 997 GT3 uses the new G97.90
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Old 02-17-2007, 07:10 PM
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if you lived in a place with fast tracks and no speed limits you wouldn't bitch about the gearing.

So complain to your track designers and your road safety authorities, rather than Porsche. Alternatively, ask PCNA for slower cars.

R+C
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Old 02-17-2007, 07:52 PM
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Originally Posted by Nordschleife
if you lived in a place with fast tracks and no speed limits you wouldn't bitch about the gearing.

So complain to your track designers and your road safety authorities, rather than Porsche. Alternatively, ask PCNA for slower cars.

R+C
Very few tracks in Germany can take advantage of the GT3's stock gearing. It's all wrong for the Hockenheimring for example.

I don't find it necessary for my enjoyment to travel 190mph on a track - 130mph is plenty for excitement as long as there are interesting turns. Those hypersonic speeds just introduce an unneccessary element of danger.

The autobahn is a different story...
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Old 02-17-2007, 10:21 PM
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Originally Posted by GrantG
.

The autobahn is a different story...
So maybe PAG is telling you something. The stock gearing is fine for the NŘrburgring, once you know your way round.

Seriously, you learn a lot about car handling when cornering at very high speeds, although there is a high pucker factor initially. Also braking hard from high speeds and dealing with lack of downforce through high speed corners is 'educational', having driven on both high speed and low speed tracks, I'll take the former over the latter any day.

R+C
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