I did a lot of research before I bought a C4 991.1 diff. Externally they're identical minus a color change on the torque tube. My 991.1 diff even had some damaged parts so I bought a 997.2 snout and it was the same length and bolted up. Stub axles are the same too between 996/997/991. The only thing I haven't verified yet is the R&P ratio in the 991.1 diff...it's on my to do list before I install it. Porsche does have the 991.1 C4 and C4S front diff spec'd as the same 3.33 (vs 3.44 rear; 3% delta) in the 997tt/997.2 but I want to spin it out and verify. Even between the C4 and C4S they run a slightly different tires size (2% delta vs 2.7% in tires)
For a square setup I'd just monitor temp and you could probably even map it with the controller via temp. Most of the times you'll need AWD will be for short sprints at lower speeds. You could map it to go more RWD with speed which should make sure to keep the temps down.

 

I will be curious to hear your findings on this when you get around to it.

Still searching for one in Canada...

 

The controller for my diff defaults to spending most of it's time open (no power to front wheels). It only sends power forward during acceleration or maneuvering. It does have a manual mode where I can "lock" the differential at any percentage of torque transfer I want. I never use this functionality except when I was playing with the car in the snow since it's not really the intended use case for this all wheel drive system.

 

RWD VS AWD...

Between RWD vs AWD which is more reliable and durable in the long run i.e. long term maintenance costs ?

Is there a big difference in handling in wet weather rainy conditions between RWD vs AWD and what are they?

Have any of you got caught out in a snow storm in either a RWD or AWD Porsche and how did it fair ?

How does Porsche's AWD system compare to Acura/Honda's Super Handling-All Wheel Drive (SH-AWD) on the Acura NSX, and Toyota's AWD systems?

 

Looking at the software, can you not program it to taper of power delivery as speed increases?

 

My 991 is very good in the snow, I do not drive the 996 in the snow - once I got caught in slush with 615s on it, did not do well at all, in fact, it was down right spooky.

That being said, a proper set of tyres would have helped the situation immensely.

 

As said I doubt there is any significant difference in maintenance expenses with AWD vs RWD. The AWD system on 996's is designed to step in when the rear has zero traction and let you steer the car. It won't do anything in super slippery conditions; you can find videos on youtube of 996's that are stuck in small amounts of snow.
The AWD is fairly magical on high speed corners though. It feels like the road angels are pulling the front of the car in the proper direction.
In any kind of snow proper tires are a must. Winter tires, plus having the engine weight on the rear tires is enough to get through a fair amount of snow. The car is low and will plow up an impenetrable wall of snow if there is more than a couple inches on the ground.
I live in Massachusetts and would not want to have a 996 of any sort as my only car. I would not want it covered in the magnesium chloride that's now used for roads. I also think that its limitations in snow, given the low ride height and lack of decent winter tires, would make it less practical. Although the roads are cleared within a few hours of the snow stopping so that may be less of a concern.

 

Slush is also an equal bugger.

 

The 997 turbo awd is what you would think an awd system should be. The 996 awd system should be called slight front assist, and that’s only when it’s new.

 

That is exactly what it does. During hard acceleration it ramps up the torque transfer quickly, then ramps it back down as speed increases.

 

So it is quite smooth then, on/off power transitions?

 

Seemless. If I turn the **** up (more **** = more aggressive/faster ramping of the torque split) it will induce some torque steer, but it can be dialed out.

 

Have you used the software programming feature?

Looks very trick.

 

I have played with it a bit to familiarize myself with it, but I have found the default maps to be sufficient for me so far. If I recall correctly I use the Tarmac map most of the time with the **** set around 40%. I also have the Rain map loaded but I've only driven the car in the rain a couple times since I installed the 997 diff so I haven't tested this map much.

 

That's good to know; it will be interesting to see (or hear from you) the differences between tarmac and rain... this is clearly more advanced than the one in the sti.