Funny you mention this... I've been told that it might be possible, I *think* it can be bolted in. However to control it properly would require an aftermarket ECU I believe, Garth mentioned to me that the ProEFI might be able to control it as it does currently support 997.

AEM has an AWD controller box on the adapter harness for the 996\997 cars. The AWD controller box in the AEM intrigues me but right now they aren't utilizing it I was told - not even in the 997 I suppose.

So far as *I* know it's not been done with either box although Garth might know more regarding the ProEFI since he mentioned it to me when I was quizzing him on capabilities.

I for one am interested in this idea but didn't see any readily available when I checked the various recycler sites I could find. I suspect cubic dollars beyond my means would be required but I'd love to see it done!

I think Tim was demonstrating some sort of locking front drive awhile back in a shop video posted but I've seen no updates. Perhaps he knows something too?

 

The numbers are correct. But in most cars, the front wheel drive isnt working anymore, especially because wrong tyre and wheel combos are installed. The frontwheels have to pull the car, means the tyres must be bigger than the rear ones. If you driving weird combos...the awd will not work right.

 

The 996 front differential is a mechanical AWD system that utilizes a viscous coupling to drive the front wheels. The 997.1 uses a similar system, although I don't know if it would be a direct swap. The 997.1 TT and the 997.2 cars use an electronically controlled system, and that would present significant challenges for a swap.

 

yeah it fits right in. just need to control the lockup, either standalone ECU, a button/switch, a hobb switch.
997.1 front drive swaps right in and fits perfectly. Tim has swapped into his red beast and into another car.

I don't know if there are any differences from .1 to .2 front drive but they do use different part numbers...

997.1 is 997.349.020.50
997.2 is 997.349.020.53

 

You are a VERY VERY BAD MAN! Tell me more about how this is done please!

Is it really as simple as an on\off sort of switch? I thought that the driveline shuffled power front and back as needed on the 997, no? Now that you have provided me part numbers I've been able to find a few of these beasties and the price is NOT nearly as high as I expected! If this is truly as "simple" as removing one and installing another then running a few wires I'm in trouble. How much of an advantage might this be for a 996? Reading this thread it sounds as if many of us aren't using the front drive now due to either wear or the wrong size tires - too short apparently? Is this a bad idea or a workable one? Is this how tim was able to film those vids showing the front wheels locked and unlocked on the lift, he never seemed to completely follow up and explain the mystery

 

Haha I can be worse. Ever wonder how 997 gets away with taller tires in the rear ?well the answer is in the front drive final ratio. On both 997 and 996 turbos the final drive in the rear is 3.44. On the 996 the front drive is the same 3.44 which is why the tire height between front and rear has to match. On a 997tt front drive the final drive is 3.33 which in combination with a shorter tire provides same wheel speed as the rear

Effectively what I am saying is you can now run 997Tt tire sizes AWD and not screw up the front drive.

 

Oh wow, hadn't even considered gear ratio, just ASSumed! Reading some of this thread it seemed to say we didn't want to run matched tires, that the viscous diff needed to see some speed difference with the front being slightly faster, I'd never heard that before. When I get my car back I'm going to be doing some math!

To run the 997 front driveline we would have to switch to taller rear tires to not screw that up if I follow. That doesn't sound too bad although I don't want a rim bigger than 18. My understanding is that the 997 front diff isn't an on off thing, that power can shift forward and back? If so then how is it signaled? Where can I go to learn more? I've seen two used ones with a quick search in the $1k range and while I'm not looking to buy right now that's not too expensive to seriously consider once I've got an ECU that can control it! Is the gear ratio the same with both generations? Tim, if you're following, did you find enough advantage doing this to be worth it on a primarily street driven car?

You guys going to Pocono?

 

well you just did two things for me saved me money from having guards build me a custom diff for the 996tt housing, and spent my money on 997.1 parts

 

Never knew that, the programming sounds like it would be a pain though.

 

well you are not doing any back end programming

- you either use an ECU like motec or Proefi with built in control and you jsut wire it up and tell the ecu when you want it on and it will do the rest
- you put a toggle switch or a button on it and manually turn it on
- or putt a hobb switch or rpm switch or speed or combination of two....

 

My rides in the snow have proven the 996 TT AWD to work amazingly well.

 

Currently I don't think the AEM can do this, the control of the front diff is in the firmware base flash for the 997 but their dedicated AWD controller could be an advantage when enabled. I'm not sure how ProEFI does their control on the 997 platform but if this is possible I'm VERY interested! Can the 996 axles and whatnot be reused? Looks like this has been done 2x and others are interested, can anyone who's done it write it up? I'd love to know how effective this is!

 

As i see it, I would like to tranfer the power to the front when the rears start to slip! But IT would be nice IF you could have switch to tell the ECU rwd only 😛

 

If the ECU is controlling the engagement then turning it off completely shouldn't be a problem. Shuttling power front to read ala Subaru DCCD might be a bit more difficult. This is where the AEM AWD controller may come into play although if the 997 platform already does this then we ought to be able to emulate it just as these ECU support that platform. I don't know enough about how the 997 controls the front diff or how the aftermarket ECU support it but I'd love to see what we could do with it!

 

Because that clutch can be set up to be proactive, since the VC cannot be nothing else than reactive. For a good launch it is needed to work from completely standstill, as you probably know since you have locked your 997 diff with a button. And the ability to stabilize the car in turns with a lockup of the diff at the correct time before any slip occurs and with a big enough lockup %. Lots of info on this system if you look up the very alike Haldex 4/5, which is to be found in lots of cars like Volvos, Saabs, Opel, VW and even Veyron. It's just progress, but that said the VC isn't a lousy unit when they work as intended, just not as good as a newer unit.

And by the way - as some stated here before the VC doesn't need to be heated extensively. All the silicone oil doesn't have to be warm to get solid, just the small amounts that are currently between the clutches as the temperature rises rapidly there and the viscosity of that oil is very progressive. I had a map over the viscosity at temps somewhere. Could be looked up by everyone if you wonder how fast solidity will happen.