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Gearbox Difference Turbo vs. GT2

fedmax

By fedmax
in 996 TT, 996 TT S, 996 GT2

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fedmax Member

fedmax

Posted
Posted

Hi there

Due to a gearbox failure I'll have a rebuild next week. I thought based on the POSES information it would be great to improve the gearbox when it's opened anyway. I was thinking about longer gear ratios and an improvement of the synchroniser rings. Porsche in Switzerland says there is no differnce. I checked the PET catalogue and I also see no difference in part numbers for the synchro rings.

Does anybody know if there is wrong information in there?

Sunnyside Member

Sunnyside

Posted
Posted

Hi there

Due to a gearbox failure I'll have a rebuild next week. I thought based on the POSES information it would be great to improve the gearbox when it's opened anyway. I was thinking about longer gear ratios and an improvement of the synchroniser rings. Porsche in Switzerland says there is no differnce. I checked the PET catalogue and I also see no difference in part numbers for the synchro rings.

Does anybody know if there is wrong information in there?

Hi Fedmax,

Sorry to hear your box broke.

I too have heard there is no difference except an LSD in the GT2!

What was the nature of your failure. What broke etc... What sort of power mods are you running and do you know how much power you were putting through it.

Frank

pierre Member

pierre

Posted
Posted

And how many km do you have on it? Mine failed at about 250'000 if I remember correctly.

About improving it, just give a call to Sportec before you take any decision. Highly recommended! If interested, shot me a pm and I'll give you a contact.

fedmax Member

fedmax

Posted
  • Author
Posted

Hi there

Due to a gearbox failure I'll have a rebuild next week. I thought based on the POSES information it would be great to improve the gearbox when it's opened anyway. I was thinking about longer gear ratios and an improvement of the synchroniser rings. Porsche in Switzerland says there is no differnce. I checked the PET catalogue and I also see no difference in part numbers for the synchro rings.

Does anybody know if there is wrong information in there?

Hi Fedmax,

Sorry to hear your box broke.

I too have heard there is no difference except an LSD in the GT2!

What was the nature of your failure. What broke etc... What sort of power mods are you running and do you know how much power you were putting through it.

Frank

The Gearbox goes to a specialized rebuild shop that also does engines and s on. It's not open yet so we do not know what's all broke. Fact is that it was not possible to downshift in any gear, upshifting worked. Clutch is fine. Small power mod to 460bhp (Sportec Power Mod 1)

fedmax Member

fedmax

Posted
  • Author
Posted

And how many km do you have on it? Mine failed at about 250'000 if I remember correctly.

About improving it, just give a call to Sportec before you take any decision. Highly recommended! If interested, shot me a pm and I'll give you a contact.

km 120'000, monday's car, lots of failures in the last 15'000 km. The dealership I'm with does work with Sportec, will sure do that next week.

Ronny

PS. small word...just saw your signature, same regular car, same hobbie, I drove RCN this year in a Peugeot 207 RC and one VLN race the 6h. Next year I'll drive 5 VLN races with my two collegues :)

  • 2 weeks later...
fedmax Member

fedmax

Posted
  • Author
Posted

So gearbox has been taken apart. A screw has got loose inside the gearbox and destroyed 5th and 6th gear and most of the synchro rings are gone too. They are now discussing with Sportec on how to improve the gearbox as it needs a rebuild anyway. One wish from my side were longer gear ratios :)

Mikelly Member

Mikelly

Posted
Posted

Any update on this? I ended up going with the taller gearing of the 997TT mainshaft and 1/2 gears... Went with steel syncros in 3-5 gears and all the rollpins (which is probably what came out by the way) are safety wired so none will every get loose and eat bits and pieces again. I also went with a Guards LSD while it was out, did the GT2 Slave Cylinder upgrade and had the CM clutch disc re-surfaced with Fibertuff material.

Mike

fedmax Member

fedmax

Posted
  • Author
Posted (edited)

Any update on this? I ended up going with the taller gearing of the 997TT mainshaft and 1/2 gears... Went with steel syncros in 3-5 gears and all the rollpins (which is probably what came out by the way) are safety wired so none will every get loose and eat bits and pieces again. I also went with a Guards LSD while it was out, did the GT2 Slave Cylinder upgrade and had the CM clutch disc re-surfaced with Fibertuff material.

Mike

Yes, the gearbox has been taken apart. I wanted longer gear ratios, unfortunately nobody could confirm that the GT2 gear ratios fit so we sticked to original parts. Also Sportec sells a long 6 gear for a ridicoulous 4000 Swiss francs which doesn't make sense. The GT2 Synchro rings are optimized for racing and thus harder to change gears with so also for the rings we exchange with original parts as I use the car on the street only. The clutch was replaced beginning of this year with a strong Sachs clutch up to 800nm.

The reason for the failure was the screw that got loose that holds the gears together.Its the one on the right hand side.

img5853x.jpg

This lead to a fialure of gears reverse, 5 and 6. Also 3 synchro rings are damaged:

img5856i.jpg

img5859.jpg

img5860e.jpg

Edited by fedmax
  • 1 year later...
ari1856 Member

ari1856

Posted
Posted

I know this is an old post, but the 997T input shaft is now a proven upgrade. It lenghtens gears 1-3 and also significantly beefs up the 3rd gear.

Gbox: http://www.gboxweb.com has many, many external and internal upgrades available. I would start with the ~$60 shift detent which helps engage gears better and helps prevent the dreaded popout issue.

I have no affiliation with Gbox BTW.

  • 4 weeks later...

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