Erik @ Carquip

Hi all,

Here is the story on the GT2 box.

This gearbox has a new 8:32 Cryogenically Treated / REM Micropolished ring and pinion in it. New steel synchros, new pinion bearing, new seals, new diff bearings, and a new 1/2 operating sleeve.

As to the gearing they are as follows:

1st 13:41 3.15
2nd 20:40 2.00
3rd 25:39 1.56
4th 26:34 1.31
5th 32:35 1.09
6th 27:24 0.89

This should make for a real nice gearbox for the track. Let me know if you need any additional information on it.

Price on this gearbox, without exchange is $12,500.00 plus shipping, usually about $200.00.


Let me know if you have any questions on this.

Thanks,

Erik Johnson
Carquip Sales
(303) 443-1343 ext 2

ca993twin

I'd buy that gearbox, but it needs oil. Too bad.

ruffy

erik,
you have mail
cheers

Geoffrey

Who built the gearbox, and was the pinion depth set with the Porsche tool and was the backlash, preload, and breakaway torque on the diff set correctly? What LSD is in the box and what are the locking rates? What brand 8/32 R&P is used (GT2 came with 3.444)? Does this box have the gear bearings with a steel cage or the plastic street cage? Does it have the steel shift fork or the aluminum street fork? Where is the gearbox cooler that comes on a GT2 gearbox? Can you post the transmission numbers? An aircooled GT2 gearbox would be something like a G50/54 (race). Plotting the gear ratios, that gearbox is more useful in a medium powered N/A race car than it is in a turbo car. The top speed is 145 which will make this gearbox very, very short. And the 6th gear ratio is too long compared to the other ratios unless it was designed for highway driving, and even then, it is 500rpm higher than a stock 964 3.6transmission. This looks like it might be an early GT3 Cup box from 1999 or 2000 when they had rod shifters.

Geoffrey

Actually, looking at the transmission pictured more closely, it looks to be a 5spd with a small ring and pinion (11 studs for the side cover). What's the story with the box? G50/03?

Erik @ Carquip

Here is a new picture of the gearbox just to make sure that I have the correct one listed. The ring and pinion was set correctly via the porsche factory tool. The gearbox is from a 1994 cup car, hence the rear shifter rod. The gearbox was rebuilt here at Carquip by a 30 year transmission specialist. The undergear bearings are the steel cage units. This gearbox did not come with a cooler, you might be thinking of a later generation of this box, something like the G96 / 88 for instance, this one has the gearbox id of G96/75 2 xxxxxxx. We purchased it originally from a gentleman that sold his car and had this gearbox as his backup. As standard protocol we rebuilt it, and had to replace the ring and pinion in it, as well as the other parts already listed. Yes the Differential was also rebuilt. Preload was set to .07 and backlash was set to .10 respectively. As to the locking rates for the differential, to be honest I did not write that in, however, I can have this checked should you be interested in purchasing this gearbox.

As to the ratios

Here is what the top speed in each gear looks like. Well I was going to put on the chart for you all but it is too big. So here is the breakdown.

7500 rpm redline, 26.5 in tire dia.

1st gear redline at 46.889 mph
2nd gear at 73.940 mph
3rd gear at 94.795 mph
4th gear at 113.084 mph
5th gear at 135.204 mph
6th gear at 166.364 mph

Hope that this information has been helpful

Geoffrey

I don't see any new pictures of the gearbox nor your gearchart (although it won't be any different than the one I posted). A 1994 Cup car has a G50/10 5spd transmission and as you pointed out would not have come with a gearbox cooler. How can this gearbox come from a 1994 Cup car but yet have a id of G96/75 which is a 996 GT3 Cup gearbox? The bottom line is that 1) This gearbox is not an authentic GT2 gearbox in number 2) Is not even close to GT2 specification 3) Has the wrong gearing for a turbo car, especially one for the track, 4) The 8:32 R&P will be destroyed by the torque of a turbo engine, and 5) does not have the internal pump and cooler a GT2 box would have had.

Erik @ Carquip

Well I can only tell you what was told to me, this does in fact have the larger ring and pinion, it does have the early G50 5-speed style first and second gearing, unlike the 996 three piece units, and while the center section may not be correct to this gearbox, it does have the correct strength to handle the hp and torque. This is a very stong and well built gearbox. As to the pics, check the original, I have changed it. Thank you for taking the time to chart the gearing out. That was very helpful, although I am curious what tire diameter you used. If you use 26.5 for your diameter, and 7500 rpm, I think that you will find that the chart will bear out differently then what you have listed. It would really depend on what everyone is using for their tires though.


I thank you for your comments though, I have found this exercise to be very educational and helpful.

Warmest Regards,

Erik @ Carquip

Geoffrey

Thanks for the updated information, the new picture looks better. You have to realize that a street turbo does not run a 26.5" diameter tire, only a 25" diameter tire and has a redline of 6700rpm, not 7500rpm, so while your gearing is more appropriate for a N/A engine in a race car, it is not appropriate for a street turbo car. Again, I think this gearbox is a 996 Cup gearbox of some variant. Was this the gearbox from Steve Alarcon?

ca993twin

I just gotta ask, although the answer may get me into a lot of trouble... what is the stock ring and pinion for my stock 993TT transmission. If I had my druthers (and I rarely do), I'd have gears that were approx 20% taller across the range. This could be most easily accomplished with a simple ring and pinion change, if taller sets were available. Anybody have this information? Are there taller ring & Pinion sets available? Oh lordy... I smell big trouble.

Geoffrey

The stock ring and pinion is a 3.44 (9:31) ratio and there is a 4.0 (8:32) options available. However, the front diff is geared for matching the 3.44 ratio, and unless you change that or remove it, you cannot change the R&P ratio. Further, the 8:32 won't last in a turbo engine.

ca993twin

Geoffrey,

Thanks for the info. And 4.0 is SHORTER than the stock ratio of 3.44, so even if it were doable, it would take me in the wrong direction. Thanks.

Geoffrey

yes. I can't believe you want LONGER gears. Personally, I think shorter gears work better with 6th being geared for highway use (street car statement). In a race car, I'd install a G50/52 with custom gears.

ca993twin

Geoffrey,

Well, I find 1st gear almost useless... you have to shift as soon as you stand on it. I always thought that the Ruf CTR gears made more sense, but that would be a horrible expense, unless a taller ring and pinion was available (and would work out properly). Oh well. This saves me a lot of headaches.

Stummel

0.6 for 6th gear is crazy.
Had 0.7 and that was already very looooooooong.

Guess you need almost double hp to reach 252mph in a 993tt or CTR2.