# Update to Haldex Woes: Winter Sucks Dragging Your Rear End Around



## Longitudinal (Nov 13, 2004)

Winter is here, and I am getting zero help from the rear wheels on my 2002 TTQ 225. Here are the facts:

1) When I am driving the car, there is no discernible assistance from the rear wheels. On hot, dry pavement, the front wheels will bark and hop under full throttle in first and second gear. On snow, it's a catastrophe--barely any acceleration with the traction control light flashing away.

2) The car spins the rear wheels when all four wheels are off the ground and the car is run in gear.

3) I do not have a VAGCOM, and would like to avoid spending $350US just to fix this problem because the problem itself is probably not going to be cheap to fix.

4) Precharge pump is new. Replacing the pump DID make a difference. Before I replaced the pump, the rear wheels would not spin under their own power at all. Now the rear wheels spin, but they aren't helping to prevent or reduce front wheel slip under load. 

5) While I was replacing the pump, I found the broken ground wire and repaired it by building something three times heavier than what was there. 

Has anybody experienced massive front wheel slip with a good, functioning precharge pump? The pump seems, in most cases, to be the first suspect.

Could the faulty pump (replaced) or broken ground (repaired) thrown a code that prevents the Haldex from working properly until the code is cleared?

Here's a note from another VWV user regarding the controller: _Haldex controller? self test said it was ok but i took it apart and found that the shaft with the rack of gears that engages the pinion gear of the stepping motor that controls the hydraulic pressure delivery to the hadex clutch, had rotated enough in its bore so that it no longer engaged the stepping motor so there was no hydralic pressure delivered to haldex clutch. I rotated the shaft and reassembled the car...up on the jacks...started the engine...engaged 1st gear and released the clutch and almost cried as all four wheels were rotating!!_

Could a controller cause my symptoms considering that my rear wheels DO spin with the car lifted?


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## Marcus_Aurelius (Mar 1, 2012)

Honestly man, you need a vagcom or become friend with someone that has it. It would make your life much easier, especially with problem diagnosis (in a 21st century way at least). 

With the precharge pump issue handled and ruled out, there is a host of other things that will prevent the system from working or simply disable it (that's where a vagcom would come in handy). As you pointed, one of the things could be a faulty controller. Mechanically, the stepper motor in the controller could go bad, and it's not unheard-of for the internal circuit board to kick the bucket on the electrical side (on high mileage units, I've even seen badly worn teeth on the plastic gear shaft that rides on the stepper pinion to couple the metal pin that promotes/restricts fluid flow). 

With that said, before you spend more by throwing parts at it, find yourself a vagcom to rule out or narrow things down. Vagcom, besides telling you about codes stored, can perform system efficiency tests. This procedure will greatly help you in narrowing down the issue (hopefully it's not worned out clutches as that's the most involving and costly repair).


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## Longitudinal (Nov 13, 2004)

I definitely understand the usefulness of a VAGCOM, and will buy one in the long term, but $350 is a substantial share of the cost of fixing the problem. Money is limited right now, so I have to focus the money I do have directly into fixing the problem. I have been hoping to find somebody who knows Haldex to help me reason through this. 

You agree that a controller is a possibility. Would a faulty controller still allow the wheels to spin when the car is lifted off the ground? 

I have been internetting the heck out of my problem, but basically all I find are people who lost their RWD, replaced their pump and lived happily ever after.


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## 20v master (May 7, 2009)

Longitudinal said:


> I definitely understand the usefulness of a VAGCOM, and will buy one in the long term, but $350 is a substantial share of the cost of fixing the problem. Money is limited right now, so I have to focus the money I do have directly into fixing the problem.


So buy a cheap ebay cable and pay the $99 license fee. Otherwise, take it to a VAG repair shop and let them charge you an hour of labor to read the codes.


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## bwdz (Jan 21, 2015)

My Haldex was kicking in and out. I ran the VAG Com on it only to get an intermittent fault code. The ground wire was broken but it still acted up sometimes after that repair. I serviced it with new fluid and filter and it is fixed now and has not acted up. My fluid was in really bad shape, no material in it but the visosity of it was so different than the stuff I put back in. I will be changing it once again at the next oil change, I suspect that some moisture got in mine but it could have also been the previous owner just had not done in a long time. 
Where are you located? I'm in Michigan and this morning it was -7 degrees and it still worked perfect. I think the viscosity of the fluid is important for proper function.


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## L33t A2 (Aug 5, 2003)

My rears did not work for my first year of ownership.
A quick scan with vcds showed me that:

Address 22 -------------------------------------------------------
Controller: 02D 900 554 B
Component: HALDEX LSC ECC 0006
1 Fault Found:
65535 - Internal Control Module Memory Error
00-00 - -

The haldex controller had failed and needed replacement, bottom line was that after swapping the controller my awd works great now. Scan the car before you throw parts at it.


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## asiwa (Dec 18, 2014)

I have my own saga of repairs that I am still sorting through to this day. My car acts exactly the same - while the car is on the lift, all four wheels will turn. On the ground and under load there is no assistance from the rear wheels. 

Basically, everything everyone has said prior to this is correct. You need VCDS. Buy the $10 ebay cable and the $99 VCDS Lite license and be done with it. They'll even let you move it to another device/computer one time if you have to change PCs. That comes before anything else. That or find someone local who can lend you theirs for the day.

As for the repair, I've done many of the Haldex-related fixes so far and no results. I still have one or two left to conduct, but here is the rundown:

1. Replaced brake light switch
2. Repaired ABS control module (was completely inoperable) 
3. Replaced ABS wheel speed sensors (originally one, now two)
4. Replaced ground strap
5. Oil/Filter change
6. Pump rebuild (parts from YourHaldexWorks, OEM stuff)
7. Inspected rear diff connectors (they were in perfect shape)

I currently have a Clutch Malfunction - Intermittent code.

That's what I'm up to now and I still have the same symptoms. A word on the pump; my original pump was still *technically* working, but sounded weak while it was on the car. I figured it had to be done at some point so I rebuilt it and it now sounds stronger. The improvement seems to be noticeable on the lift but again there is no effect in real world driving. I too was hoping for the same miraculous pump repair, but alas I was not so fortunate.

Being that the list is getting shorter and shorter, I had a conversation with ChrisLP1, who is a regular on the R32 forum. He and I chatted a bit about some of the more involved and complex issues that can arise with the coupling. 

He mentioned something interesting; even if the controller has set the valve to completely open and there is no force against the clutch packs, the drag from the parts inside will be enough to spin the wheels while the car is off the ground. In effect such a test is not particularly conclusive. He has experience replacing the actual clutch packs inside of the Haldex, which require very very extreme wear and track/dyno abuse to reach the point of total failure. He recommended that I swap out my Haldex controller for another to eliminate that as a fault, so that will be my next item. 

VCDS doesn't test the controller as faulty, but there are a multitude of things that can go awry with it. The stepper motor inside that moves the pressure valve can fail. The electronic board itself can fail. The gear shaft can fail. The wiring can wear down and oil can actually leak out of the module and down the wiring if a seal goes bad. The connector for the module that is mounted on the back of the diff can become corroded and damaged. All of that makes the controller a very common failure point in the system while simultaneously being incredibly difficult to diagnose unless there is a complete failure of the electronics. 

Once you get your car scanned you can take it from there. That will hopefully narrow your search some and you'll be able to perform the Haldex output tests and read some block values. That will all give you some helpful information.

Edit: Didn't see it mentioned, but did you do a fluid/filter change? When you do make sure to check for particles/debris in the fluid. A couple flecks here and there are normal, but exorbitant amounts of particles and gunk would be a bad sign; in that event you could have some clutch pack damage but unless the car was abused before you owned it there would be no reason to suspect that.


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## Longitudinal (Nov 13, 2004)

Asiwa,

Thank you for a thoughtful answer. Yes, I changed fluid and filter with the Haldex pump last summer. 

Your remark about the ability of drag to move the rear wheels without meaningfully driving them makes sense, but my problem started with zero rear wheel motion before I replaced the pump. With new pump, I have rear wheel motion but no rear wheel assist. 

If I am replacing the controller, I want to upgrade it at the same time since I will be doing that anyway in order to get acceptable performance of the Haldex. Suggestions on controller brand? **EDIT** It appears that most Haldex performance stuff does not include a new controller. Didn't somebody offer a whole replacement performance controller?

I'll order the cable and software.


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## L33t A2 (Aug 5, 2003)

Longitudinal said:


> Suggestions on controller brand? **EDIT** It appears that most Haldex performance stuff does not include a new controller. Didn't somebody offer a whole replacement performance controller?
> 
> I'll order the cable and software.


Yes, that was a long time ago. There was a Blue "performance" controller and an Orange "competition" controller.
Used prices on these was in the $800-1300 ($1000 average price) range until last year when HPA and United Motorsport released software flashes for the stock controller. Both look to be $700 at this point in time.
I bought my stock used controller from a junkyard in South Carolina for $75 plus shipping ($90 total) which I found via www.car-part.com (Part is referred to as "computer box not engine - transfer case". I did have to re-pin both connectors to use it which was a bit time consuming and delicate process. I'm happy enough for now with the stock controller's performance, but if I had to pick from the two current aftermarket upgrades I would pick UM just so I didn't have to deal with some sort of option touch panel. IMO a good chip should do it all without my input to tailor it to my needs. If I'm paying money for something it should just work and self learn/adapt to the throttle input and conditions.


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## Longitudinal (Nov 13, 2004)

Long absence from this thread, but now I have scanned for codes. Result: NO CODES. 

No codes.
New pump.
New filter.
New fluid.
Rear wheels spin when lifted car is run in gear.
Front tires blow apart under heavy acceleration on dry pavement.

Is it possible at all to have a bad controller and not have a code?

A friend mentioned the possibility that somebody did something dumb like flash the ECU with a FWD performance tune. Could something like this cause a Haldex problem? Seems like totally separate systems, but I'm grasping at straws here. 

When I changed the Haldex fluid, I drained, changed filter, filled with new fluid until fluid ran back out the fill plug and closed it up. Is there such a thing as a bleed of the system? Would I need to top off the fluid once the system has been run?


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## bwdz (Jan 21, 2015)

Maybe the clutches are worn and won't hold a big load, just slipping and that's why it will spin on a hoist but not when large amounts of power are applied. I have 185k miles on mine and it still holds well on wet or dry pavement so I don't know if that's possible to wear them out like that but maybe.


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## Longitudinal (Nov 13, 2004)

Clutches have long been my suspect, but I have always been told that they basically last forever, and that when they do fail, they weld.


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