If the AWD system works then it is always “on”. If your AWD is not working then you have other issues and would need to diagnose what’s causing the AWD not to work. It can be a number of things that can cause the AWD to not work. Your car has poor AWD system where the AWD typically fails.


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If the AWD system works then it is always "on". If your AWD is not working then you have other issues and would need to diagnose what's causing the AWD not to work. It can be a number of things that can cause the AWD to not work. Your car has poor AWD system where the AWD typically fails.

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What i mean is to keep awd on when not losing traction. I have heard some people that have done something to their awd to make it be activated when not losing traction. Sorry should have clarified more.

 

If I'm correct it's always a 90/10 split and up to 60/40.
But
Vdveer is a custom controller that overrides the stock.

They are still working on the S60R Gen2 system. There is a workaround you can buy this system to make your own. Gen2 from VW is on the Mk5 R32 part number 1K0907554 direct swap on your Haldex diff.

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vd Veer engineering car electronics. Haldex, DSG, CAN controller and other CANBUS devices.

www.vdveer-engineering.nl

 

If I'm correct it's always a 90/10 split and up to 60/40.

It can go from 100/0 to 0/100.

Volvo made a big point of demonstrating that their all wheel drive system could accelerate a car if only one tire had traction. That would be 100% torque output to one wheel and 0% to the other three. If it was 90/10 or 60/40, then you would need traction at both ends of the car to go anywhere.

 

With gen 2 haldex, which is what's in the 04 Rs, I don't think this is possible without some compromises.
The haldex has a clutchpack that transfers power from the haldex input (driveshaft from angle gear which is always powered) to the output (rear differential then to rear wheels.) The clutchpack is engaged by hydraulic force. The hydraulic force in the gen 2 haldex is generated by a mechanical pump that runs when there is a difference in rotational speed from the haldex input shaft to the output shaft. I don't think sustained clutchpack lock can be easily achieved in this system. If the input shaft and output shaft are spinning at the same speed (locked clutch) then the mechanical pump is not being driven and no more hydraulic clamping force can be generated. The clutch can't be locked from a dig either, requires front wheels to be moving.
Gen 3 (05-07 Rs) is mostly the same but has a slightly different pneumatic circuit which allows the electric feed pump to momentarily generate the hydraulic working force to engage the clutchpack.
Gen 4 does away with the mechanical speed differential style hydraulic pump and uses the electric pump to generate the force to engage the clutchpack.

One of the things I was wanting to work on when I get time was to see if the gen 4 haldex from some xc90s will bolt in to my 04 R. If so, I could attempt to control the feed pump and solenoid in a way that would offer a more aggressive amount of power to the rear wheels.

 

With gen 2 haldex, which is what's in the 04 Rs, I don't think this is possible without some compromises.
The haldex has a clutchpack that transfers power from the haldex input (driveshaft from angle gear which is always powered) to the output (rear differential then to rear wheels.) The clutchpack is engaged by hydraulic force. The hydraulic force in the gen 2 haldex is generated by a mechanical pump that runs when there is a difference in rotational speed from the haldex input shaft to the output shaft. I don't think sustained clutchpack lock can be easily achieved in this system. If the input shaft and output shaft are spinning at the same speed (locked clutch) then the mechanical pump is not being driven and no more hydraulic clamping force can be generated. The clutch can't be locked from a dig either, requires front wheels to be moving.

Is there not a solenoid that maintains the hydraulic pressure to keep the clutches engaged after the pump generates the initial pressure from the difference in rotational speed?

I'd be curious to see more of the internals or at least a diagram of the wiring and hydraulic paths.

 

The easy way to picture it is this, imagine the front tires are completely off the ground. The front tires are still spinning, but there is zero torque being transmitted through them. 100% of engine torque is going to the rear wheels. The Haldex system is capable of this.

Just because something is spinning doesn't mean it is getting torque, and just because something is getting torque doesn't mean it is spinning. Torque has no motion to it, you can apply torque and never move a single degree of rotation.

It is true that the rear tires will never be able to have more SPEED than the front tires, but that's okay. Between the front end's greater turning circle, and the front tires' smaller rolling radius due to heavier weight on the front, the front tires should always have more speed than the rears anyway.