Posi Rear Ends

[Wbulk]

Shortly I will have to order the Posi differential for my Ford 9". Over the years I have had both friction disc type and a Detroit Truetrac. The Truetrac was really purchased due to it's outstanding performance in the snow. Recently, I have heard that some guys are putting the Truetrac in their Cobras. Let me be clear I am not talking about lockers for a Cobra but just limited slip differentials. I have no experience with the performance of either of these in a light Cobra car. My experience has been on trucks.

Friction Disc or Cone Type
The friction type for the most part puts equal presure to each axle until one of the axles overcomes the force of the springs and discs. Once that force is overcome it allows the wheels to turn at different speeds for like going around corners. These have a long standing track record, but do wear out over time. This type usually needs a friction modifier added to the gear oil for smooth operation.

Detroit Truetrac
This is a gear type system that transfers traction to the wheel with the most traction. If one tire is on a wet slippery surface and starts to spin, the gears in the differential transfer the power to the wheel with the most traction. One minor shortcoming of this system is that it needs some traction or resistance on each wheel to work. So if one wheel was off the ground a light brake presure may be required get the traction to the wheel that was on the ground. This system seems to need little maintenance other than regularly changing the gear oil.

I am interested in experiences of each of these installed in a Cobra. Are there known pros and cons to a light weight vehicle? How do they effect handling?