Haldex Quattro Controller...Advice Needed!


Low life livin' the high life.
Feb 9, 2008
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Hello all.... I've already posted this in the A3 8P forum also. I need a little technical advice from you very knowledgeable people:

I have recently been reading up on replacing the Haldex Quattro controller in my A3 2.0T Quattro S-line. For those of you who don't know (as i understand it - correct me if i'm wrong!!)...
A3's, TT's and Golf R32's/4motions use the Haldex form of Quattro. This system feeds most of the power (70-80%) to the front wheels (basically to save power/fuel at low speed and when cruising). When the rear wheels begin to slip under cornering or acceleration the Haldex system throws more power to the back wheels.
This is different to the A4, A5, A6, A8 (and R8?) which employ the Torsen Quattro system. This is a much more pure form of 4WD and has an even distribution of power to front and back wheels at all times.

SO.... I understand that by simply changing the Haldex unit which comes in an A3 as stock, you can dramatically improve the 4WD performance of the car and make it handle like a 'proper' quattro. The improved Haldex system puts more drive to the rear at all times and throws additional power to the rear much more readily.

My question is...where's the best place to get an upgraded Haldex unit for an 8P A3? Am i right in saying they're approx £550 - £600 + fitting?
As you are only replacing the existing Haldex part for a new one, will it affect the warranty on the car??
Has anyone already done this modification? Are there any potential pit falls i need to watch out for? Obviously tyre wear and fuel economy will suffer but the handling of the car should be superb compared to the stock 4WD setup.

Any feedback would be most appreciated! Thanks in advance guys.

Cheers for that, seems a decent price compared to some i've seen.
Will you really notice much difference? Seems alot of money/time when decent tyres and geometry settings would probably help more?
Unless you drive on slippery country road or do track days i don`t believe so. I do have one fitted and the TT shop is the best place to get them from as they are European disruptor's for the uprated Haldex controllers.
apparently it does change the nature of the car quite a lot if you drive it on the limit and there's a lot less of a shunt as the haldex transfers the torque back and forth (based on a friend's comments on his tweaked R32).... also changing down into a corner and using the engine-braking to balance the car through the corner and to then accellerate out is a lot more predictable and it will keep the car a lot more balanced.

Not tried it myself - my Golf is FWD and the A4 is straight Quattro, not Haldex.
My understanding from previous posts on the subject is that Haldex can only transfer a maximum of 50% to the rear wheels while Torsen can be configured to put as much as 100% to either end.

I also believe that in normal conditions Haldex equipped cars are almost 100% FWD. However I guess a revised controller can be configured to send more power to the rear in normal conditions.
Pretty sure haldex is capable of sending 100% of torque to either axle.
Any confirmation on this ??

i also believed that haldex could only transfer 50% power to the reat wheels??

Also i was under the impression than an s3 (8l) is full time AWD.... ??
Ed at APS can give you some info on this also, must admit its something I'm considering as a future mod, the last approx quote I had was in the region of £800 fitted, lightly more for the switchable variety that gives you a controller wired into your dash/centre console.
There are different versions of Haldex, 4 in the VAG arena as far I know but I think Gen4 is still in development. There are plenty of others out there ie Volvo, Saab (cross drive), Ford Kuga, etc.

Each has different capabilities and improvements over the older generation. From reading about Haldex from the peeps that make it (some US engineering company) it can transfer nearly all the power to the rear but runs in almost FWD mode until slip is detected at the front wheels and thats when torque (Haldex is a torque transfer system) is passed to the rear; how much, for how long and how aggressively depends on the input signals and the progamming of the Haldex controller - this is happening all the time and unless you deliberately put the car into a controlled slide you can't really tell its happening*

You can get 3-mode aftermarket controller which have different settings, ie comfort; sport; race or something similar. EIP used to have one for around £400 !

I'm on my 3rd Haldex based car (R32, GTTDI 4MO and A3 TQ) and have owned Torsen based Audis before. The short wheelbase of the transverse engined cars is much better suited to the Haldex system... no need to be 4WD if the conditions don't require it.

* However, its quite possible to get some of the rear-end-out 4-wheel driving action on the go if you learn how to initiate the Haldex and catch the car at the right time.
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Haldex is a Swedish company. 100% power cannot be drive. To the rear as there is no center diff, the front wheels are permanantly driven with a transfer box driving a prop to the rear, the rear diffs input is controlled by the haldex clutch which can only give as much power as the front is getting but never any more. Was thinking about getting one for mine but due to no center diff the drive front to rear is not independant, personally I think the transfer box would be under too much stress