I haven't put a lot of km on it yet but the difference is noticeable. Launching is great - no wheelspin, it just goes. Cornering is more neutral and you can feed in the power harder and earlier than in the fwd car. Its very confidence inspiring. Mind you there's a lot of suspension work in it as well so that helps but its certainly more competent. Where it absolutely shines is in the wet as the grip is enormous.
At the moment mine is sub-optimal as I'm running all XR5 modules (PCM, ABS, Yaw) so technically they don't know there is a Haldex module out the back. The Haldex is sitting on the HS CAN so it will do its thing based on the data it collects off the network but I'm not convinced the other modules are doing anything with the data out from the Haldex. I'm surprised it works as well as it does. My concern is that if you got into trouble, the ABS will still act as a fwd while the Haldex may still be driving the rear so the car could become unpredictable/uncontrollable.
If one wanted to use the correct set of modules you need a Kuga PCM, ABS & Yaw sensor then it all works as per the factory programming in the Haldex. IDS correctly sees all the modules however in a Ford you're then stuck with a Kuga tune which at 200hp is pretty sad. No one does custom tunes (big hp ones) for a Kuga so then you have to get someone to write one, and by then you may as well go aftermarket ECU. I went EMU Black because they do a modified Haldex which basically hands over control of the stepper motor to the ECU. I had RaceHead Engineering do mine at the same time I bought the Black. Lastly you can't mix a Kuga ABS with a XR5 PCM because Ford code the part numbers into the software so if it doesn't get a match you get a bucket load of errors.
For the rear diff as you know the Gen IV Haldex is the better one as it has a preload factor plus the programming takes more notice of throttle position so responds quicker. I have already got the Racing Diffs (Serbia) Gen IV Haldex plate upgrade pack ready to install. Looking at the Quaife while the overall dimensions are the same as the Kuga diff centre, the location of the crownwheel on it is quite different between the Volvo and the Ford. So I'll use the Volvo diff but mount the Gen IV Haldex on the front. Other things I've learnt - you'll need an external oil cooler on the Haldex oil to keep it cool otherwise once it gets to 100C it shuts down and you get no drive. The other thing to look at is our diff is the same one used in the Freelander 2 and in the UK they have a problem with pinion bearing failure. There is a company over there that specializes in fixing the issue and they do that by machining out the housing and fitting a larger bearing in place. Haven't found anyone out here that does that but surely can't be too hard. The diff bearing failure is partly related to oiling and the transfer case pinion apparently suffers the same. My thought is to plumb both cases for external oil coolers and have the return feed as close to the bearing as possible. Its all going to be trial and error but you have to start somewhere.
