964 C4 lt wt manual differential control's

[911st]

I have long been curious about the manual controls that Porsche put in there Light Weight special C4's and offered to some of there race customers and was hoping for some input on how the early C4 drive train works and if I might be on the right track.

I used to think the special adjustment system was something very special and complicated but studying the picture of it below I am thinking it might not be that complicated and could be copied relatively easily.

I suspect the C4 diffs have a slave cylinder on them that takes pressure from an ABS style pump and valving controlled by a special ECU.

Looking at the picture of the C4 lt wt's system it looks to me like it is two fabricated manual adjustor's that probably have a master cylinder of some type bolted to the back of each of them.

Then, with adjustment the master cylinder would pressurize the slave cylinder at the differential and effect the level of lock up.

To give the driver some form of reference it also looks like they plumbed in two 25 bar pressure gauges so it is known how much adjustment has been applied to each diff.

If this is so and someone just wanted to, why couldn't one even just fabricate and replace the slave cylinders with a mechanical adjustment at the differentials and mechanically fix the amount of lock up for a track car?

Dose this make sense? Any input appreciated as I am not very schooled in this system.

[911st]

It looks like I got it right. Following is from another thread.

Dose anyone reconize the master cylinder like is it from the clutch, brakes or something else?

Originally Posted by MyTurbo3.6

RUF C4 Torque Splitting Bias...


















"Unique RUF System for 964 and 993 Porsche C4 models: Cockpit Adjustable Torque Bias

You've heard of adjustable brake bias front to rear. This is the same concept, except the driver can turn a knob (next to gearshift - see photos) to move more of the torque to the front wheels as needed or desired by putting pressure on the center differential.

Dash-mounted pressure guage allows to driver to guage the torque split/bias based on the level of pressure shown.

RUF says the range is 5% front / 95% rear on up to 40% front / 60% rear. From a performance standpoint, its a nice aid to adjusting and dialing in the handling characteristics of the car.

The installation of the torque bias control is relitvely simple. It
involves installing the hydraulic cylinder on the center console and
connecting it to the brake fluid resivoir. And then connecting the slave
cylinder on the transmission to the master cylinder that has just been
installed on the console."

[rs27carrera]

Has anyone done this to his/her 964 C4? I would be tempted :-)