# How do you test a Haldex AWD to see if the rear wheels are getting traction?



## MEDEL514 (Jan 12, 2002)

I have a 2001 Audi A3 (8L) 1.8tqm, same drivetrain as the TT. I'm posting here because the A3 forum is a ghost town. 

Now that the roads are getting slippery in the morning, the car slides alot more. I'm still riding on summer tires, just need to pull the winter tires out of the basement and swap them. I was playing around the other morning when it was wet and very cold/frosty and I was launching the car from several stops and roundabouts. I noticed that my front tires would spin alot while launching every time and I felt no push or help from the rear tires.

Does this mean that the driveshaft isn't sending power to the rear axle? How can I check to see the power distribution to the rear wheels? The center diff is electrically controlled, right? How can I check that the center diff is actuating like it should? This is my first Haldex AWD and I already kinda don't like it. I've had a few Torsen AWD's in the past that seemed to work flawlessly all of the time. I'd like to get this figured out before the snow really starts falling and I need the AWD to get up a hill to my house. Thanks!

Pic for clicks!


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## fredclan (Jul 2, 2007)

*hope its a fuse*

I had the same problem when I bought my first Audi. Was a used 01 tt 225 six speed and I knew nothing about it. Front wheels spun on wet pavement. I put it up on jacks and only the front wheels spun although some will say this is not a good test. There is a fuse that protects the electronics, check that first...mine was good. I next hooked my vag-com up and performed a self test and it showed all systems good? I got under the car and found that a small electric pump sometimes called a "cargo pump" was inop. Corroded and expensive, i found a used one and installed it...so excited ....still no AWD. ugh...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!!Took me months to sort through this...good luck...hope its a fuse.


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## Scigano (Mar 10, 2011)

VAGCOM is a good place to begin to make sure there aren't any issues with your Haldex system. The benefit of it being electronically controlled is that it can store and show codes for pending issues like the ECU.

Here's a post for a mechanical inspection of the Haldex unit from Audi Forums


Haldex diagnostics and function testing....
First run a VAG-COM diagnostic on the AWD system. A bad controller or connection issue will likely show up here


Mechanical Function-test of the Haldex coupling. 

- Rollout in circle

Aim: Check the function of the coupling and the response on the car. Is to be done on level ground.

1. Drive in circle with minimum turning radius at a speed of about 10 km/h. 
Disengage the clutch and close the throttle. 
Let the car roll to full stop.

2. Drive in circle with minimum turning radius at same speed as in case 1. 
Disengage the clutch and run up the engine to 3000 - 4000 rpm. 
Let the car roll to full stop.

* If the coupling is working the car will stop in about half the distance in case 2 compared with case 1.

* If there is no difference in the two cases there is a malfunction of the coupling. The problem could be caused by the coupling or by missing signals from the car. A further inspection has to be done to be able to determine the cause of the malfunction.

* If a noise from the HLSC is noticed when turning or driving in circles the oil in the coupling is damaged. The damage can be caused by overheating or by water in the oil. 


- AWD test on car lift. (all wheels free to turn.)

Aim: Check the function and the control of the coupling.

1. Pull the handbrake. 
Disengage the clutch. 
Start the engine.
Put the gearbox in 2:nd gear.
Let the engine idle. 
Engage the clutch.

* Engine is supposed to stop when the clutch is engaged. (HLSC controlled as in handbrake start.) If engine do not stop, disengage the hand brake immediately. Otherwise there is a risk of seriously damage on the HLSC.

2. Disengage the handbrake.
Disengage the clutch and start the engine
Put the gearbox in 2:nd gear.
Let the engine idle. 
Engage the clutch. At least one front wheel and one rear wheel is supposed to turn.
Pull the handbrake for 2 seconds. 

* Front wheel is supposed to turn while the rear wheels are supposed to stop when the brake is pulled. Engine is supposed to run all the time. (HLSC controlled as in handbrake turn.) Don't exceed the 2 seconds or repeat the test for more than 5 times during a 5-minute period. Otherwise there is a risk of seriously damage on the HLSC.


Trouble shooting on HLSC

- Visual inspection 

Aim: Check for leakage and external damage that affects the function on the HLSC. Is to be done with the car on a car lift.

1. Check for oil-leakage from the coupling. If leakage is found, check oil level at the level screw on the left side of the coupling.


2. Check wires and connecting sockets.

T8 - Socket between car and control unit
T8/1, Red = Ign.
T8/2, Black = Gnd.
T8/3, White = BLS
T8/4, Blue = HBLS
T8/5, Brown = K-line
T8/7, Blue/Grey = CAN low
T8/8, Blue/Orange = CAN high

T2 - Socket between control unit and feeder pump
T2/1, Yellow = Pump 1
T2/2, Yellow/Black = Pump 2


- Signals 

Aim: The following signals from the car affect the function of the HLSC. If one or more of the signals is missing or false the function of the HLSC will be reduced.

Bremse 1; BLS, BTS, ABS 
Bremse 3; VR, VL, HR, HL


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## MEDEL514 (Jan 12, 2002)

^^^ That's an excellent write up! Thanks for that info!!!



fredclan said:


> 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...good luck...hope its a fuse.


Do you remember which fuse to check? Knowing my luck, it wont be a fuse! I ran the Haldex system self test through the VAGCOM too and everything came back fine. Where exactly is the stepping motor is mounted on the transmission? 

I'm waiting on a new ABS sensor to come in, should be here this by weekend, and then I'm taking the car to the auto hobby shop on a lift to check a few other things on my list of minor discrepancies. She's an old car with ~350K km's, but I love how she drives and she still looks great! I want to keep her in tip top shape for another 350!


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## MEDEL514 (Jan 12, 2002)

i did the AWD tests with the car on the lift, and the rear wheels didn't spin in any senario. Again, the haldex test through the VAGCOM came back good with no faults. I couldnt find which fuse to check either. 



fredclan said:


> 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!!Took me months to sort through this...good luck...hope its a fuse.


 So i was under the car this weekend trying to find this stepping motor on the rear diff and i could figure out which part it is. iremoved a cylyndrical looking component held in by two 4mm screws, but it was some kind of oil filter screen thing, no shaft coming out of it. can you give me some more info on this stepping motor that you checked?


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## MEDEL514 (Jan 12, 2002)

Here's a picture of the part i removed between the axle and gas tank, from the front side if the rear diff. It was held in by two 4mm screws. Is this the Cargo Pump that pressurizes the diff oil??

UPDATE: This part is called the cargo pump, just an electric motor that pressurizes the Haldex oil.









Here's the read diff, looking towards the back, where I removed that part. Some of the gear oil came out when I pulled the part out, but not much. 









Here's the part again showing that filter screen thing. No shaft on this components.


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## MEDEL514 (Jan 12, 2002)

fredclan said:


> 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.


 Is this where the stepping motor would be, near or behind the Haldex controller?


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## l88m22vette (Mar 2, 2006)

Excellent Haldex/rear diff dissection thread

Enjoy


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## MEDEL514 (Jan 12, 2002)

l88m22vette said:


> "http://www.ttforum.co.uk/forum/viewtopic.php?f=2&t=202454"


The link doesn't work?  

Looking at this picture I'm guessing the haldex coupling gear oil is separate from the rear diff, does it take the same 75W-90 oil? where is the fill plug for the coupling? i need to get my car figured out soon. thanks for the help!


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## Scigano (Mar 10, 2011)

Woah, woah — there's two oils we have to change in the rear differential?  I've only been changing the Haldex fluid.


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## MEDEL514 (Jan 12, 2002)

Yeah, they are separate cases. I just got an Audi A3 Maintenance Manual sent to me from another forum member, and the manual says to use 0.25 liters of G 052 175 A1 oil in the Haldex. I don't know if that's any different from the 75W-90 gear oil that I used in the rear diff. 

But at this point, I can't find anything online to point me in the right direction to fix this FWD problem, I've found may documents and thread on various sites especially ttforum.co.uk, but there seems to be so many different things in the Haldex system that could be wrong to cause this FWD issue. So I'm about tempted to just take the car into the dealer and have them do the AWD troubleshooting and Haldex oil and filter change at the same time.


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## crazybohunk (May 24, 2011)

MEDEL514 said:


> Yeah, they are separate cases. I just got an Audi A3 Maintenance Manual sent to me from another forum member, and the manual says to use 0.25 liters of G 052 175 A1 oil in the Haldex. I don't know if that's any different from the 75W-90 gear oil that I used in the rear diff.
> 
> But at this point, I can't find anything online to point me in the right direction to fix this FWD problem, I've found may documents and thread on various sites especially ttforum.co.uk, but there seems to be so many different things in the Haldex system that could be wrong to cause this FWD issue. So I'm about tempted to just take the car into the dealer and have them do the AWD troubleshooting and Haldex oil and filter change at the same time.



Hi there,

Ok I have a few threads on this subject but I will give you my two cents on this problem.

First off yes there is diff fluid and Haldex fluid.

Your problem is probably not your diff or the fluid for the diff.

Changing the Haldex fluid on your Haldex unit although a very good idea on a regular basis along with the filter will probably not fix your problem.

That pump you took apart that you have photos of in this thread is called the Cargo pump or pre charge pump.

If the pump is shot or in your case KAPUT you have no Quattro.

They fail on a very regular basis. Ask me how I know:banghead:

It pressurizes the Haldex fluid when the car is running so that when the controller thinks you need all wheel drive it engages the Haldex clutch and now the rear wheels have power.

Since you have the pump out already take it apart & if the electric motor is full of gunk/ grease then its dead.

Buy a new one install with the new Haldex fluid and filter and away you go.

Give it a try.

Good luck

Randy.


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## Scigano (Mar 10, 2011)

crazybohunk said:


> First off yes there is diff fluid and Haldex fluid.


How often should the rear-diff fluid be changed? And does it use anything particularly special, or do I just put the same stuff that's in the front transaxle?


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## fredclan (Jul 2, 2007)

sorry i didnt get back to you sooner.. put some power to your cargo pump and see if it spins, you'll feel it...its pretty quiet. you can ititiate a vag com self test of the AWD system and have someone under the car see if it cyces on and off. You mention an abs sensor and im not sure if a bad one would interrupt AWD controller. it takes alot of inputs from the cars sensors. I think I unbolted my haldex controller and hooked it up and ran the self test and thats when i noticed stepping motor working but hydraulic relief valve pin not moving... schematics and diagrams available somewhere.
good luck

Ted


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## fredclan (Jul 2, 2007)

fredclan said:


> sorry i didnt get back to you sooner.. put some power to your cargo pump and see if it spins, you'll feel it...its pretty quiet. you can ititiate a vag com self test of the AWD system and have someone under the car see if it cyces on and off. You mention an abs sensor and im not sure if a bad one would interrupt AWD controller. it takes alot of inputs from the cars sensors. I think I unbolted my haldex controller and hooked it up and ran the self test and thats when i noticed stepping motor working but hydraulic relief valve pin not moving... schematics and diagrams available somewhere.
> good luck
> 
> Ted


ps
stepping motor and bypass valve pin are in hadex controller. basically, the haldex clutch engages the rear axle when hydraulic pressure squeezes the haldex clutch. the hydraulic pressure is pumped whenever the front to rear driveshaft spins at a diferent speed than the rear axle ( wheel spin). the amount of hydraulic pressure reaching the clutch pac is determined by a bypass valve in the haldex cotroller. full bypass = no AWD. it is the job of the haldex controller to take inputs from the cars many sensors and decide how much pressure to send to haldex clutch by positioning the pin in the bypass valve via activation of the stepping motor. The pre charge pump or cargo pump basically keeps a small amount of pressure to keep fluid moving through the systemso that on demand is quick.


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## MEDEL514 (Jan 12, 2002)

crazybohunk said:


> That pump you took apart that you have photos of in this thread is called the Cargo pump or pre charge pump.
> 
> If the pump is shot or in your case KAPUT you have no Quattro.
> 
> They fail on a very regular basis. Ask me how I know :banghead:


 I already had the car reassembled when I posted these pictures, but I may take it back up on the lift and have a look again. Is there a way to test the cargo pump without a VAGCOM? I only ask because I know someone with a VAGCOM who is usually busy, he already tested my Haldex system and it came back with no problems, but I didn't know to go under the car and listen for the pump. I'd like to look at the possibility of the pump a bit further before taking it into the Audi dealer for troubleshooting. Should I, or can I apply 12v directly to the pump to test it while I'm under the car? I'm only guessing that the pump is 12v. I wish there was a Bently manual for the A3 so I could have my own references.


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## crazybohunk (May 24, 2011)

MEDEL514 said:


> I already had the car reassembled when I posted these pictures, but I may take it back up on the lift and have a look again. Is there a way to test the cargo pump without a VAGCOM? I only ask because I know someone with a VAGCOM who is usually busy, he already tested my Haldex system and it came back with no problems, but I didn't know to go under the car and listen for the pump. I'd like to look at the possibility of the pump a bit further before taking it into the Audi dealer for troubleshooting. Should I, or can I apply 12v directly to the pump to test it while I'm under the car? I'm only guessing that the pump is 12v. I wish there was a Bently manual for the A3 so I could have my own references.



Hi there,

Well with Vagcom you can run the test program and it will start the motor and you should be able to hear it spinning.

However on one I tested it would barely spin. On another one I tested it would spin sometimes.

So I would have traction sometimes and then nothing for the rear.

I had two defective ones I experimented with. One on the car and another complete diff with the pump and haldex unit I bought for testing purposes. 

On the brand new Cargo pump( precharge pump) I bought I tested it on the bench and put 12 volts DC to it and it spin's strongly and you can hear it very clearly and when I had it installed you could still hear it very clearly when tested with Vagcom.

So yes with a couple of probes and some DC power you should be able to power the pump up by attaching to the connectors if you want.

This fixed my problem totally and even with a larger turbo and stage 2+ tune I get no front wheel spin now.

It hooks up immediately on both dry and wet surfaces.

When I disassembled the old pre charge or cargo pumps the actual electric motor was full of grease like gunk that had penetrated the seals and contaminated the motor with haldex fluid.

This is not fixable you would have to chuck it and buy a new one like I did for a solution.

Randy.


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## MEDEL514 (Jan 12, 2002)

ok, I just wanted to make sure the pump was 12v before putting voltage directly to it, thanks, I will be going back to the hobby shop this weekend to take the parts out again. Hopefully I can confirm the cargo pump bad so I don't have to take the car to the dealer just yet.


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## MEDEL514 (Jan 12, 2002)

I took the cargo pump out again and shot 12v to it using an AC adapter and the pump didnt come on. I thought maybe the AC adapter didnt have enough power to turn the pump so i got out some jumper cables and applied power directly from the battery and the cargo pump still didn't come on. So I think I can safely say that the cargo pump is shot. I will be searching for one online and crossing my fingers that it fixes the problem. 

On a side note, sine I have to take the pump out again, I may as well change the Haldex oil and filter. I don't have a filter wrench, so how hard will it be for me to DIY? And do I use the same 75W-90 as in the rear diff? Thanks!


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## crazybohunk (May 24, 2011)

MEDEL514 said:


> I took the cargo pump out again and shot 12v to it using an AC adapter and the pump didnt come on. I thought maybe the AC adapter didnt have enough power to turn the pump so i got out some jumper cables and applied power directly from the battery and the cargo pump still didn't come on. So I think I can safely say that the cargo pump is shot. I will be searching for one online and crossing my fingers that it fixes the problem.
> 
> On a side note, sine I have to take the pump out again, I may as well change the Haldex oil and filter. I don't have a filter wrench, so how hard will it be for me to DIY? And do I use the same 75W-90 as in the rear diff? Thanks!


 Hi there, 

Well this confirms my suspicions about your pump. 

Yes you need a new pump and new Haldex fluid and filter when you install the new one. 

The Haldex fluid is separate from and different from the rear differential fluid. 

The part number from ECS tuning for the kit is G052175A1-KIT 
http://www.ecstuning.com/Search/Haldex/ES3070/ 

Since you are in Germany you may not want to buy it from ECS in the US. You can go to their web site and it has photos of the kit and fluid & which should allow you to figure out what you need from the local Audi dealer supplier. 

The wrench is helpful to get the filter off. 

I have seen some people make their own homemade version of it to get the filter off 

It is in a very tight area. Without the tool putting on a hoist would allow for easier access to it. 

Good Luck 

Randy.


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## MEDEL514 (Jan 12, 2002)

Thanks for all of your help! I am going to change the filter and oil and I get the new motor, I have been doing alot of searching and found that people are using the cargo pump from the Volvo haldex units because they are half the price of the VW/Audi pumps, I would just have to splice in the connector to work on my Audi. Might be a good alternative to save me $300! 
Cheaper Haldex pump replacement!


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## MEDEL514 (Jan 12, 2002)

MEDEL514 said:


> Cheaper Haldex pump replacement!



Just wanted to update this thread for the archives. I went and bought the Volvo Haldex Cargo pump and did the swap as shown in the link above. I did this on my 2001 Audi A3 1.8tqm which is the same as the Audi TT and similar to the R32. I bought the Volvo pump from a Volvo dealer in the states that ran me about $260 for the pump and shipping. I also bough Haldex oil and filter from ebay to change as well as the Haldex filter wrench to aid the Haldex filter install. I read that the Haldex oil and filter should be changed every 20k miles, so I'll be needing the wrench again. I did a quick solder (black to black, and brown to yellow) to put the Audi connector on the Volvo pump, slight turn of the new pump's housing to clear the wires of any chaffing, Haldex oil servicing, and I got all 4 wheels spinning again as soon as I started the car!! :laugh::laugh::laugh:










NOTE: there is some speculation that the Volvo pump will not work because the pick up filter is in a different position that the Audi's, but given the amount of Haldex oil in the unit, I presume the pump's pick up filter would be submerged at all times regardless of pick up filter position, and the pressurized fluid (inbetween the two O-rings) would enter the Haldex unit with no problems. My test confirms that the Volvo pump cured my 2WD syndrom and saved me over $300 for the OEM Audi pump! Mark this one as a win! :laugh::laugh::laugh:

Thanks to all of you who replied and helped point me in the right direction for fixing my problem! I hope this thread helps someone in the future who has that crappy 2WD syndrom like I had! :wave:


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## l88m22vette (Mar 2, 2006)

Nice to see you took the chance and it worked, though I'd like to see more info on the part differences (an illustration of the Volve part would be cool too). Glad the car works again 



Scigano said:


> Woah, woah — there's two oils we have to change in the rear differential?  I've only been changing the Haldex fluid.


Yep, and there are two places to worry about trans fluid, both the actual transmission and the bevel box, which is where the driveshaft connects. You should change both at same time, about every 60k


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## esoxlucios (Sep 17, 2009)

Scigano said:


> VAGCOM is a good place to begin to make sure there aren't any issues with your Haldex system. The benefit of it being electronically controlled is that it can store and show codes for pending issues like the ECU.
> 
> Here's a post for a mechanical inspection of the Haldex unit from Audi Forums
> 
> ...


Easiest test I've found is to jack the car up on the front on both sides using an ordinary floor jack with roller iron wheels. Then, in first gear, very, very gently attempt to partially engage the clutch. If the Haldex is working, the car should attempt to lurch forward slightly (from torque being applied to the real wheels).


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## jbrehm (May 16, 2006)

esoxlucios said:


> Easiest test I've found is to jack the car up on the front on both sides using an ordinary floor jack with roller iron wheels. Then, in first gear, very, very gently attempt to partially engage the clutch. If the Haldex is working, the car should attempt to lurch forward slightly (from torque being applied to the real wheels).


Whoa - are you actually recommending that someone jack up the front while leaving the rear tires on the ground, then engage the clutch to see if the car tries to drive off the jack stands?


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## esoxlucios (Sep 17, 2009)

jbrehm said:


> Whoa - are you actually recommending that someone jack up the front while leaving the rear tires on the ground, then engage the clutch to see if the car tries to drive off the jack stands?


I'm not recommending anything. I'm just saying that I've used this technique several times over the years, and has been the perfect test to make sure the Haldex can put down to the rear wheels. If you're using two floor jacks and they're both have wheels, they will roll. However, you don't need to move the car even an inch. You only need to confirm that it's trying to move, which you can feel and usually hear a creak.


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## SteveCJr (Aug 3, 2008)

esoxlucios said:


> I'm not recommending anything. I'm just saying that I've used this technique several times over the years, and has been the perfect test to make sure the Haldex can put down to the rear wheels. If you're using two floor jacks and they're both have wheels, they will roll. However, you don't need to move the car even an inch. You only need to confirm that it's trying to move, which you can feel and usually hear a creak.


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## SteveCJr (Aug 3, 2008)

This thread came up in a search I was doing. Some great info. I believe I am having the same issue as I too feel like I have excessive front wheel spin.


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## MEDEL514 (Jan 12, 2002)

Put your car on a lift and see if all 4 wheels spin. Check the power to the circuit before you drop the $$$ on a new electric pump.


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## elparcerocolombiano (Jul 20, 2006)

*Is this normal?*

hello guys, bringing this topic from the graveyard...

is this normal????

https://www.youtube.com/watch?v=FGFDoNcF0t4

I'm having the same issue with my TT. 

thank you:beer:


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## B1-16V (Aug 5, 2002)

elparcerocolombiano said:


> hello guys, bringing this topic from the graveyard...
> 
> is this normal????
> 
> ...


I am by no means a TT expert, in fact I'm currently shopping for my first one. But what you're looking at is open differentials. A stock FWD or RWD only car will do the same thing. The ability for one side to turn while the other is sitting still is what makes a car docile around sharp turns. It's that whole "outside wheel travels a longer distance than the inside wheel" thing. But it is most certainly a compromise for traction. Some would call a FWD or RWD a "One Wheel Drive" and an AWD/4WD a "Two Wheel Drive" for this reason.

If you were to lift opposite corners of most cars, including AWD, the car would go nowhere. This is where modern Traction Control is nice - it sees that one or 2 wheels spinning, and applies breaking to just that one (like you did with your foot) and allows the car to keep moving.

Now, the question that others here can answer that I can't is this - is there a limited slip (some used to be called "posi-traction") available for these cars? Again, maybe with traction control it's not as important, but still nice to have.


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## IshDog (Oct 26, 2013)

*Haldex Help*

Any recommendations on mechanics (not the dealer) in NJ and surrounding areas that are experienced in Haldex on MK1: 

Here is where I am at: 
1. Had control unit failure code, so replaced the control unit with a used unit.
2. Got the dreadful code, sporadic mechanical clutch failure.
3. Replaced the ground strap/earth wire and tested the functioning of the rear wheels.. they spun on the lift and not under load.
4. Finally got the cargo/Pre-charge pump replaced and tested in the rain the other day. Just front wheels spinning.
5. We did the VCDS test on the Haldex system and all was ok. No codes at all.
6. Traction control light goes on when I got on the car.. ABS breaks tested/AWD System test and no codes. Tried getting the wheels to spin with out EPC activated with no luck either.

Is there anything else this awesome community can tell me what to look for before I get under the car myself and replace the whole rear drive of the car with another used unit? Thinking checking fuse #31, all electrical connections and there was something above stated by the 2nd poster??

163K on 2002 ALMS EDITION and don't think car is worth more than 4k.. Sucks to be attached to a fun car!


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## IshDog (Oct 26, 2013)

fredclan said:


> I had the same problem when I bought my first Audi. Was a used 01 tt 225 six speed and I knew nothing about it. Front wheels spun on wet pavement. I put it up on jacks and only the front wheels spun although some will say this is not a good test. There is a fuse that protects the electronics, check that first...mine was good. I next hooked my vag-com up and performed a self test and it showed all systems good? I got under the car and found that a small electric pump sometimes called a "cargo pump" was inop. Corroded and expensive, i found a used one and installed it...so excited ....still no AWD. ugh...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!!Took me months to sort through this...good luck...hope its a fuse.


Can anyone elaborate on this above? I replaced the cargo pump with a new one.. is there something I am missing?


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## JoshFerguson (Feb 19, 2020)

I'm waiting on a new ABS sensor to come in, should be here this by weekend, and then I'm taking the car to the auto hobby shop on a lift to check a few other things on my list of minor discrepancies. She's an old car with ~350K km's, but I love how she drives and she still looks great! I want to keep her in tip top shape for another 350!


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## thieblak (Dec 16, 2020)

fredclan said:


> *hope its a fuse*
> 
> I had the same problem when I bought my first Audi. Was a used 01 tt 225 six speed and I knew nothing about it.
> 
> hey just did the same thing what was actually wrong with the system that you fixed. I tested it in snow and only front wheels spun.


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## IshDog (Oct 26, 2013)

Not sure if I updated on this thread, however posted my results on another.. For me it was a break light switch $10 at VW dealer! Lights always worked, however something about the communication with the whole Haldex System was failing after all this expense. Here is a good tech guide if it can help. 









Haldex Service Training – Self Study Program


I recently have been lucky enough to put my hands on the VW Haldex Service Training – Self Study Program (no. 89C303). And since I get a lot of questions about it, here’s the integral d…




auditttuning.org


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