Hi Guys, I have a friend with a 2004 GT3 who wants to change his gearbox internals to shorten the ratios of his car. He wants to change the 4th, 5th & 6th gear ratios. Have anyone of you guys done this? Do you guys have the part numbers for the shorter ratio-ed gears? Do you guys know what parts are involved? Thanks.

 

RS Patrik has done this!

Ciao,
J.

 

https://rennlist.com/forums/showthre...1&page=2&pp=10

 

Here is what I got when asking the same question to the forum:

https://rennlist.com/forums/996-gt2-gt3-forum/283611-wich-new-gear-ratio-for-my-gt3.html

 

I've done it on my 05 Gt3. 2-6th with 5th moved to 6th position. In combo with lwfw and cup lsd, it transforms the car and really keeps the engine in its sweet spot. Nice that this was done with all Porsche Motorsports components. One of the best mods I've done on any car I've owned and especially nice on gen2 GT3's. However, not inexpensive.

 

There are 2 methods by which we perform this mod.

Here's a cut and paste from our soon to be released TRG product guide:

TRG Porsche GT3 Street Production Car Transaxle Upgrading

As Equipped by Factory:
The Porsche 996 GT3 production street car has a tall geared transmission. The stock MPH ratings for each gear of the GT3 are:

Gear MPH
6 190+
5 171.8.3
4 141.7
3 110.1
2 79.6
1 45

Track driving, flying starts, and standing starts benefit from shorter gearing. “Gearing down” lowers top speed by raising the RPM level for a given gear selection, while improving response to power input. TRG changes gear ratios in the 996GT3 to optimize the use of the vehicle on racing circuits. TRG offers 2 options for changing the GT3 transmission gearing. Additionally, a limited slip differential upgrade can easily be added to both of the TRG gearing options.


Option 1
Install existing 5th gear into 6th gear position and replace 3,4,5th with aftermarket gears.

Aftermarket gears are available in race finish; normal usage noise will be more audible than that of the stock Porsche street car gears. While 3-5 will sometimes exhibit a whine or hum, the 6th gear will remain quiet for top gear freeway driving and fuel saving cruising.

Re-Gearing Top Speed Chart
Gear MPH
6 171.8
5 146.3
4 121.9
3 101.1
2 79.6
1 45
$3900, includes parts and labor. May require shipping charges.


Option 2
Remove and replace 3.44:1 (31:9) stock ring and pinion with 4.00:1 (32:8) ring and pinion.

Replacing the ring and pinion of the GT3 transaxle with a 4:1 ratio unit retains the original gears and will not result in abnormal noise. Net effects are remarkably similar to changing and replacing transmission shaft gears with highly regarded reliability. TRG uses the Porsche Motorsports 996 RSR ring and pinion set for best quality.

Gear MPH
6 172.6
5 147.9
4 122
3 94.8
2 68.5
1 38.7
$4250 includes parts and labor. May require shipping charges.


Differential
The stock 996 GT3 limited slip differential unit has no pre-load and is designed with ramping. Ramping means the lock up increases as load is applied to the unit. The stock suspension and tires do not achieve enough load to make full use of the stock LSD unit. The stock unit has no immediate effectiveness, and too much slip can occur during corner transitions. Stock 996GT3 ramp rate is published to be 40/65% lock up at full potential.

TRG offers a preload lock up solution that results in an “always active” LSD unit. While this solution may not be ideal for street driving (parallel parking and rain understeer in particular), the tighter LSD unit can bring down lap times and make better use of the GT3’s drivetrain. Ramp remains; however, lock up begins immediately and is always on.

Add $265 to any transmission re-gear or R&P replacement...."while you're in there".

Recommendations
TRG recommends using TRG 996GT3 suspension upgrade components to enhance communication between driver and vehicle, make better use of the GT3’s capabilities, and limit active alignment changes.
§ Replacing rubberized suspension components with metal connections allows better sensory input from car to driver, and more precise reaction from driver to car input.
§ TRG suspension upgrade components, from bushing removal to full 4 way adjustable damping, improve handling and the ability to effectively transfer power through the GT3 LSD and tires.
§ Active alignment changes occur from rubber flex in shock towers, control arms and toe arms. TRG spherical bearing shock towers and toe links greatly reduce flex and improve road/track feel.


Austin

 

Looks like for a slower track, combining methods 1 & 2 would make for a mean combo (Lower R&P plus closer ratios 4-6). This would seriously compromise top speed and freeway cruising revs, but it would be a quick S.O.B.

 

Austin I looked for your sorry *** yesterday around the TRG rig. Were you there?

 

JRG, you old timer, I was everywhere yesterday, touring all around, was at the transporter, went to turn 1 for IMSA Cup, back to transporter for lunch time, then up to the corkscrew for Speedvision GT. Great weather yesterday. Were you at the Porsche corral?

 

Austin, swapping the R&P costs more than replacing gears?

 

Hey Holger,
The price differential in the two operations is mostly the parts delta. RSR ring and pinion is the way to go to keep the box consistently quiet and maintain original gears on the both shafts.

Austin

 

Thanks for posting Austin...its great to get it "from the horses mouth".

 

One more benefit from the shorter R&P is that the shorter 2nd gear is very useful for auto-x. There is good spacing between 3rd and 6th with the stock gears.

 

NJ-GT, did you do the R&P change or the re-gearing?

 

Another option is to change the 1st/2nd gear shaft when changing the R&P. Using the cup car shaft, which has taller gears, makes 1st and 2nd more effective on the street and shortens the gap between 2nd and 3rd.

Jim