2fcknfst

I didn't know it snowed much in Greece.

Must be global warming.

Carlo_Carrera

Global cooling.

Third-Reef

Small correction, the 996TT doe not have a viscous differential between the front and read. it has a viscous coupling in the front drive shaft. This allows the rear wheels to spin without the front differential seeing any rotation at all, just a variable amount of torque applied to it depending on the coupling conditions. So rear wheels can spin and front wheels do not spin is quite common in the normal operation of the AWD system of 996 TTs

Carlo_Carrera

I think there always at least 5% torque going to the front wheels via the coupling.

indesj01

How does all this compare to 997 system ?? Does the 996 system have any advantage over 997 or 991?

Dock

Correct.

Carlo_Carrera

997 system is controlled with an ECU and electronic clutches, 996 system is pure mechanical via the viscous coupling. Both have their "advantages" and they feel a bit different. It really comes down to personal preference.

indesj01

Can you feel the difference in that does the 996 handle as good? Without a limited slip in the rear or axle diff lock how does the system handle slick cornering conditions?

jumper5836

Had a friend with a 996 C4S burn out his front diff doing donuts on wet pavement. In my experience 3 times had full front awd activated, once in my 996 C4S hitting coolant in middle of a intersection turning left, it saved the car for me because I did not know it was there and I was accelerating quickly from a red light and hit it.Next C4S and a stop sign on a back road and pavement was very sandy again under full acceleration. On my Turbo hitting coolant on track one rear tire hit drove through it and power was sent to the front. Every time it has done it, It feel like I just blew the engine and power was only 40% the 60% is gone and it really feels slow and takes a few seconds to get full power again and feel normal. I am not sure when front is 40% that any power is going to the rear at least not something you feel.

Carlo_Carrera

If both cars are in stock configuration the 997TT handles better in all conditions.

If you add a set of aftermarket Ohlins R&T coilovers to the 996TT and a limited slips dif IMHO the 996TT rides and handles better than a stock 997TT.

But they still feel different. The 996TT is very analog car. The 997TT is the beginning of electronic nannies. The 997TT also has electronically controlled shocks. It just a different car, still a 911 Turbo but different than a 996TT. Both are great for their own reasons.

pancing

Without lsd or lockers youll just veer a bit. With lsd youll just spin tires. With awd you dont really need lsd as awd pulls if your rears spin.

rwd is a different story.

indesj01

then what does the rear axle lock differential do on the awd 997 tt do?

pancing

They lock up when one wheel spins so the other wheel gets you traction. It helps but you dont NEED it in an awd car. The only time when you really really need diff lockers is if you have a rwd solid axle.

Correct me if im wrong but doesnt 997tt have elsd?

cdk4219

Limited slip differentials don’t really lock up, but apply torque to the wheel that is spinning. For a “live” solid axle car it is much more beneficial because the engine torque lifts the right rear wheel. An independent rear suspension differential is attached to the car without springs so the twisting motion is contained to the chassis, and doesn’t lift the right wheel, although the 911 would lift the left rear wheel since the engine is backwards.

I would guess that a lot of these viscous clutches are worn out, I know the one in my old 996 was pretty much non functional, as the wheels wouldn’t even spin on packed slippery snow. The inside wheel would however spin in a corner and the traction control would come on.

pancing

Yep.