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Hi,
My 964 was originally a C4 before I totally got it dismantled and totally being converted to a race car now.
This transformation happened in several steps that started around 2003, so almost six years ago.
During two years, I found some information because I was thinking of keeping 4WD, or maybe 2WD using the original 4WD PDAS (which is also used for ABS), and yes it is possible. I've even seen several cars converted like that in France.
First of all, the 964 4WD system may be criticised here and there, but it looks to be a really good system, that has been simplified for the 993. I helped some guys who used it on an off road endurance race car in France in the late 90's, it was very efficient.
If you just disconnect the mechanics (remove transaxle and front differential) the PDAS won't like it and just block the car with a set of 'blonk' noises if you turn the wheels and slipper.
The G64 transmission has two controls : longitudinal (rear/front), and lateral (left/right, but rear only) tork repartition. These controls are managed by the ABS valve controller located in the front compartiment of the car, which the booster and the pressure accumulator.
The ABS valve controller have basically 5 chanels : 2 front brake lines (left/right) one rear brake line, and two tork control lines.
These tork control lines don't exist on a C2. On controls the front/rear repartition, and the other one controls the rear left/right repartition.
I don't know if the C2 has two different brake lines for the rear wheels, or only one like on the C4?
A funny thing to do (I did it) if you replace the G64 transmission for a G50 is to keep the LSD from the G64 and modify the G50 case to receive the hydraulic piston that manages the left/right tork control.
You need to short-circuit the 5th channel of the valve control (the one that used to manage rear/front) and the car runs!
There is nothing on the front diff. that can tell the PDAS/ABS brain that the differential is missing. It's all passive. Only the hydraulic valve has to be bypassed.
When the rear wheel slipper (the brain will know it because of front ABS sensors telling it that those don't spin, and because of the accelerometers in the center console in case of drift) the brain will open the front/rear chanel to release more tork to the front, but it's not a kind of expert system that will check the result of its actions.
The rear is different, because the brain takes care of the right/left control and will be upset if locking the rear differential has no effect (then it clonks all time and the motricity is bad).
So from my point of view, the cheaper and more interesting conversion would be :
- buy a G50 (RS or 6 speed one with LSD).
- buy a pair of front 993 C2 hubs - a good opportunity to upgrade the brakes ;-) You may need 993 ball joints for the tie rods. I'm not sure the 964 joints have same diameter that the 993 ones.
- open the G50, sale the LSD.
- remove the whole G64 transmission, remove front C4 hubs.
- install front 993 hubs.
- bypass exit 5 (the one that controls the front/rear tork repart.) on the ABS valve control system.
- open the G64, take the differential. Sale the rest for parts.
- Get a machinist to make a hole on the G50 case to receive the hydraulic piston that controls the lateral tork repartition.
Then you have a Carrera 2 with an electronic motricity control, the rigidity of a Carrera 4, and the wide body... cool car.
Yes, it's some money for the parts, and a lot of labour - so a lot of money again if you don't do it by yourself.
On my G50/64 gearbox, since it's a race car that won't use any original ECU nor PDAS/ABS, I plan to install a lateral screw that allow me to adjust the LSD (I had that on a car 20 years ago and loved it). Not sure it will work, since it's not designed to be a linear but actually an on/off system. I have to open it and see how it works again.
Hi,
My 964 was originally a C4 before I totally got it dismantled and totally being converted to a race car now.
This transformation happened in several steps that started around 2003, so almost six years ago.
During two years, I found some information because I was thinking of keeping 4WD, or maybe 2WD using the original 4WD PDAS (which is also used for ABS), and yes it is possible. I've even seen several cars converted like that in France.
First of all, the 964 4WD system may be criticised here and there, but it looks to be a really good system, that has been simplified for the 993. I helped some guys who used it on an off road endurance race car in France in the late 90's, it was very efficient.
If you just disconnect the mechanics (remove transaxle and front differential) the PDAS won't like it and just block the car with a set of 'blonk' noises if you turn the wheels and slipper.
The G64 transmission has two controls : longitudinal (rear/front), and lateral (left/right, but rear only) tork repartition. These controls are managed by the ABS valve controller located in the front compartiment of the car, which the booster and the pressure accumulator.
The ABS valve controller have basically 5 chanels : 2 front brake lines (left/right) one rear brake line, and two tork control lines.
These tork control lines don't exist on a C2. On controls the front/rear repartition, and the other one controls the rear left/right repartition.
I don't know if the C2 has two different brake lines for the rear wheels, or only one like on the C4?
A funny thing to do (I did it) if you replace the G64 transmission for a G50 is to keep the LSD from the G64 and modify the G50 case to receive the hydraulic piston that manages the left/right tork control.
You need to short-circuit the 5th channel of the valve control (the one that used to manage rear/front) and the car runs!
There is nothing on the front diff. that can tell the PDAS/ABS brain that the differential is missing. It's all passive. Only the hydraulic valve has to be bypassed.
When the rear wheel slipper (the brain will know it because of front ABS sensors telling it that those don't spin, and because of the accelerometers in the center console in case of drift) the brain will open the front/rear chanel to release more tork to the front, but it's not a kind of expert system that will check the result of its actions.
The rear is different, because the brain takes care of the right/left control and will be upset if locking the rear differential has no effect (then it clonks all time and the motricity is bad).
So from my point of view, the cheaper and more interesting conversion would be :
- buy a G50 (RS or 6 speed one with LSD).
- buy a pair of front 993 C2 hubs - a good opportunity to upgrade the brakes ;-) You may need 993 ball joints for the tie rods. I'm not sure the 964 joints have same diameter that the 993 ones.
- open the G50, sale the LSD.
- remove the whole G64 transmission, remove front C4 hubs.
- install front 993 hubs.
- bypass exit 5 (the one that controls the front/rear tork repart.) on the ABS valve control system.
- open the G64, take the differential. Sale the rest for parts.
- Get a machinist to make a hole on the G50 case to receive the hydraulic piston that controls the lateral tork repartition.
Then you have a Carrera 2 with an electronic motricity control, the rigidity of a Carrera 4, and the wide body... cool car.
Yes, it's some money for the parts, and a lot of labour - so a lot of money again if you don't do it by yourself.
On my G50/64 gearbox, since it's a race car that won't use any original ECU nor PDAS/ABS, I plan to install a lateral screw that allow me to adjust the LSD (I had that on a car 20 years ago and loved it). Not sure it will work, since it's not designed to be a linear but actually an on/off system. I have to open it and see how it works again.
My two cents.
Thats worthy 2 cent read! Thanks. I'm starting to look at the costs of changing certain parts of the G64 and converting it to a G50. Apparently this can be done?
Since a lot of people are asking for it, this is my best estimate based on a full conversion except the hydraulic booster for the brakes (the RS has this too)
I am in the middle of it so not all is known yet.
Last edited by Jan911; 03-10-2024 at 07:15 PM.
Reason: replace estimate
When i did this some years ago, i was able so source a G50 with a bad synchro and had the box refreshed and regeared and fitted a new LSD. In the end, the box was roughly 10k and the whole job with new C2 driveshafts and a CAE shifter was roughly 18k euro just the parts, without the profit of selling the old C4 stuff...
G64 became also quite "expensive" in germany, i was able to sell mine for 2,5k last year...
In 2001 I bought a new 6 speed for $2500... new not stolen. Gave it to a friend for cost. So ignorant.
I could have bought multiple 6 spd boxes at that price. But I had just closed the Porsche business from 9-11-2001 wiping it out.
Crazy. I sold my spare a couple years ago to a member here. THe one I have for my tip swap was said to be a new porsche unit that sat in a project that never got finished. It's not LSD so when I pull it apart, I will see how new it really is. I asked here and it seem, at least, the AT at the end of the serial number indicates that it was not delivered in a car but rather sold over the counter or replaced an otherwise defective original unit. I bought that 4 years ago...if I had to buy it today, it might make me second guess this endeavor.
03-09-2009, 02:10 AM
