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Audi TT Quattro 225 Haldex Issue

30K views 62 replies 11 participants last post by  Christian_02_225 
#1 ·
Hello, i am new to this forum and have heard positive things about it. I have a 2002 Audi TT Quattro 225 and I love the car despite the usual Audi problems, other than that, the car runs great and there is no major problems with it. My Haldex system does not seem to be performing correctly, I have put it on jack stands and all 4 wheels spun but I get bad wheelspin or power loss from ESP when driving "spiritedly". I know it is engaging but do not think it is providing sufficient torque to spin the wheels from the weight of the car since it did spin on the jacks but does not feel working on the street. I do not know the last fluid change, but there is fluid inside, and considering the car has 170k on it with a rebuilt motor, I expect some problems but would like to at least find out what is wrong with the Haldex since it is a major feature to the car that i am missing out on. Any advice would be appreciated Thanks!
 
#2 ·
Hey man!

First of all, welcome to the forum. We do have a great community here and I hope you'll find everyone's advice both helpful and insightful.

The Haldex system in the MK1 TT can be glorious at best and downright frustrating and maddening at worst. Especially with such a high mileage car, I would recommend checking out the following things:

-Haldex fluid/filter - make sure you do a change right away. The fluid/filter service is something that owners and even dealers tend to forget about and could have been neglected for a long period of time. You can get the tube of fluid and filter from any Audi/VW dealer .

- ESP/ABS Codes - Bad sensors and ABS modules account for a fair chunk of Haldex issues. If either system is working incorrectly and throws a code in the ECU, the system will drop to front wheel drive only until the parts are replaced and the codes are cleared. These codes can be checked with VCDS/VAGCOM.

- Haldex control module - The physical computer module that controls the pressure on the clutch pack is notorious for failing due to exposure/vibration/fluid leakage/etc. This is the problem that my particular car had. The modules can be bought new for way too much money or you can find one used fairly easily for under $200. Make sure you get one off of a low mileage car, if possible. Also be sure that it wasn't chopped off (check pictures to make sure that the cables and connectors are intact). The module can be read for codes and tested for functionality from VCDS as well.

Other small assorted issues - any part that is interconnected with the Haldex system can cause problems. Things like the brake light switch under the brake pedal, clutch pedal switch, and the ground strap that connects the Haldex casing to the car chassis can all cause the system to fail. Most of the solutions are straightforward, but diagnosing the actual problem can be the hard part. VCDS is your best friend, if you can get it or have access to it.

I'm a bit short on time and don't have the ability to write more at the moment, but if you have questions or want specifics feel free to ask. Everyone here is happy to help!

Sent from my Nexus 6P using Tapatalk
 
#3 ·
Hey, thanks for the quick reply, there are not any codes according to the obd ii scanner i have but the ground strap on the haldex was disconnected when i first go it and fixed that, but like i said, the haldex IS engaging but i guess once on the ground, it just doesnt have enough pressure on the packs maybe? Would an overdue filter/fluid change cause these symptoms? Once again thanks for the reply and advice.
Thank you
 
#5 ·
The issue you're experiencing is actually identical to the problem I was having. My car is an early '01 225QC, so it doesn't have ESP and the previous owner(s) didn't opt for that part of the recall.

MC is right about getting the fluid and filter done. I am personally doubtful that the fluid itself is the cause for malfunction, unless the system was run dry or almost dry and caused excessive heat and wear which is a rare occurrence. I do have a whole shpeal that I give about the Haldex but it's better at this point to take the issue one solution at a time.

Sent from my Nexus 6P using Tapatalk
 
#6 · (Edited)
Okay guys thanks for all of the replies! I do recall trying the rollout in the parking lot and I did not do it correctly if i remember right, but I did hear a sound similar to a power steering pump but with out the whine, and also it sounded like something was dry and heard a variety of very light clicks and taps. I am pretty sure that this sound was the haldex trying to engage but it did not sound so healthy:confused:. It is too late as of right now to go test it again but I will do it the proper way, and let you guys know! I am probably going to do the fluid/filter change. How difficult is this process and what am I looking at as far as price? Thanks again guys!
Oh and one time I did crack the drain plug slightly open just to make sure the system was not bone dry, and there was indeed fluid in it, but i do not know what kind of viscosity the haldex fluid is supposed to have but it seemed relatively thin in my opinion.
 
#7 ·
Fluid and filter is NOT something you should "probably" do - it is the ONLY think you have available as your next step. There is NO Point in doing any other troubleshooting at this point until you change the fluid. It should not be thin, it is relatively thick, and if the viscosity is wrong, or if the fluid is contaminated, or ... your Haldex won't work right even if EVERYTHING else is fine.
 
#9 ·
As I recall from my last fluid change, the Haldex oil is actually very thin and runny even when fresh. It sloshes around fairly easily in the factory container. Used fluid will be even thinner but really not by much - if anything it will just be slightly darker from regular wear inside the system. All of this is a result of the "oil" not actually being oil in the first place; it is hydraulic fluid that is used to apply pressure to the clutch plates.

The above comment is also a route to check out; I completely forgot to mention the precharge pump. That was another fix that I took care of and while mine did need to be replaced, it was ultimately not the prevailing issue with my car.
 
#8 ·
The clutch plates are usually pretty tough so the usual culprit is a weak charge pump when the wheels just won't grab. It would be good if you posted up your location and someone who has VCDS can scan it for you, your OBDII scanner is not scanning the Haldex system. VCDS lets you run a test on the system and shut the pump on and off from your laptop as well as test communication with the controller. You can drive down the road with VCDS and see if all your ABS sensors are reading the same Etc....
 
#10 ·
Okay I have finally done the oil change. Like I expected, no difference. I started researching a bit more and have came to the conclusion that I am pretty sure my pre charge pump is weak. I have put the car on jack stands before and the wheels spin, but since there is no resistance to the rear wheels since the car is in the air, I think that the precharge pump may be weak, since it is for a fact engaging, I just maybe think that it could be old and worn out and not providing sufficient pressure to the rear wheels. Any help will be appreciated and I heard these motors are pretty pricey, I also heard that ordering a Volvo haldex pump will be much cheaper. I do not need OEM or anything, but I just want my haldex to work. And with me considering a chip, maybe APR or REVO, I would really like the extra traction. I feel like I am missing out on a fun feature of the car, and would really like to make this thing work. Thanks
PS what chip do you guys recommend for reliability, and performance gains (yes i know both are rare) but input is appreciated Thanks again
 
#11 ·
SO you think your awd is not engaging, but it did on jackstands. One simple test you can perform before going any further would be this, go drive down the road "spiritedly" like you mentioned so that the esp kicks in from tire spin, go back, pull the haldex fuse which will definitely disengage the awd and do it again. See if it is much different or if it is about the same. This would tell you if it is working at all or not at all.
 
#13 ·
Where are you located, many of us have VAGCOM and can scan the system for you. If you want, send me a PM with your email and I can forward you a PDF file of the factory service procedure with all the pinout readings you need to get on the plugs and the test and service procedure.
 
#14 ·
Okay, it has been a while since I had been concerned about this Haldex Unit, and out of the blue last night I was browsing eBay and found a complete haldex carrier assembly for only 179.99 plus shipping which was 125. I ended up getting it for 149 plus shipping by making an offer. I had to snatch it since they are usually 500-600 dollars or more, and it came with a 6 month money back guarantee. My question would be, how difficult would it be to swap the entire carrier assembly, and could you refer me to a write up on it? Thank guys
 
#15 ·
That's definitely priced significantly lower than most rear assemblies I've seen, but I am really questioning the desire to swap the whole assembly out on your car (assuming you haven't done any further troubleshooting).

These problems are usually due to a failure of one or two very small electronic components in the Haldex system as a whole. This purchase means you have a spare in the event that your rear end implodes, but that really doesn't happen on these cars unless you:

- Run the system with no fluid
- Never change the fluid or filter (even then the innards are pretty hefty)
- Abuse the car on a dyno
- Abuse the car on the street
- Use a poorly implemented aftermarket Haldex pressure controller

In light of this, swapping the rear end on your car will absolutely be more work than it's worth. Did you try rebuilding/replacing the precharge pump or swapping out the controller? Both of those fixes take far less time and hassle and are almost always the cause of malfunction.

Also - I have seen rear assemblies on ebay in the past for that price and they *always* have had the Haldex controller removed prior to being sold. Did you make sure this one you purchased had that *very important* part still attached?
 
#16 ·
Well the reason I replace the whole thing is becuase; number one, I dont wanna go through all of the work doing possibly clutch packs, pump, controller, etc and still not have a functioning haldex system. I would rather spend 275 and do it once and have it work guaranteed, than spend 200 on a pump, 70 on fluid and filter and clutch packs are i am sure an expensive unit too. Plus the work to split the haldex open and actually make it work. I saw the low price and i just had to take it. I really just want this AWD to work. Mainly becasue i have a 225HP and low profile front tires so traction is limited. I also don't like having to push the ESP button everytime I want to go fast without getting the boost cut. Not that there is any snow in South Carolina but I just would rather have AWD working because im planning on taking it to the drag strip and without the haldex working, then I would have no chance. It would have less wear on my front tires, better launches, and not that annoying traction control power cut. Thanks for your consideration though. It sounds like you know your way around Haldex units so when I get mine removed if you want to snag it you might wanna take it off my hands. It just depends, if it is something simple like the precharge pump, then I will just send it somewhere to get the motor fixed and then maybe sell the unit for a good price. I mean could I atleast get 150 bucks out of my broken one as is? Anyway thanks again. Tell me what you think, oh and is there anywhere i can find a guide to removing it and reinstalling it? Thanks !!!!!
 
#19 ·
Oh that is a big difference and probably tore up your system, I know they say that it is allowed but your rears are nearly an inch taller. BTW, running a smaller tire on the front which carries 60% of the weight of the car vs the rear is not recommended and will make your car handle extremely poorly, any car that is front heavy should not be running a smaller tire in front.
 
#20 ·
^ Im with this guy.

Staggering your tire width while maintaining uniform height all the way around is one thing, two entirely different tire sizes is another.

You're essentially running a tire setup for a chevy camaro, not a primarily fwd car with awd secondary. Like bwdz said, at BEST you're looking at 60/40 distribution, what sense does a taller, meatier tire in the rear make?

I'd spend the $275 to get some matching tire sizes, then go from there. I'd rather drive in a properly balanced fwd setup than understeer/traction/esp nightmare mode. You would be suprised the difference having matching wheel speeds will make in a system that is constantly looking for them.

Sent from my LG-H811 using Tapatalk
 
#21 ·
Not sure if you have VCDS, but if you do pull up your ABS sensors as you can read them individually. When the car is in a straight line as I am driving I am reading the exact same reading on all of mine but if my rears were an inch taller the computer would constantly be trying to adjust for the slip. Maybe your system is not burned out it's just fighting readings that are off.
 
#22 · (Edited)
Here's my post in the U.K. TT forum.
http://www.ttforum.co.uk/forum/viewtopic.php?f=2&t=1413065

Here's Video.
https://youtu.be/2I31rD3t35s

While you're in this area check the flat grounding cable found no the driver side above Haldex. My was heavily corroded and it was easy to clean up and replace with new wire.

I'm sure the rear diff fluid is well overdue and need to replace as well. Unbolt the top/side fill plug first before drain plug. Just incase fill hole is stuck.
 
#23 ·
Okay guys I havent checked on here in a little bit but just to recap, the haldex works while on jackstands but doesnt kick in like it should on the ground. I will be solving the tire diameter issue by putting 245 35 18s on the back and according to a website that is a complete diameter match to my 215 40 18s in the front. I am changing the rear end regardless, I am not interested in trying anything else on this old haldex in my car now. I would rather do it once and have a guarantee to have it work than to just to keep shooting in the dark. thanks for the input but i have just had enough with it. Thanks
 
#25 ·
I think I can speak for most TT owners when I say that we all understand your frustration with the Haldex issues, but one of the points I tried to make was that even after purchasing an entire rear assembly for your car there is absolutely no guarantee that things will be any different.

I asked if you knew if this assembly came with a working Haldex controller and didn't receive an answer. If it comes with a bad one, or doesn't come with one at all, you will be in the exact same place you were before but will be out of a lot of time and work. This is why members recommended finding someone to try and diagnose your car with VCDS. One scan can sometimes tell you exactly what's wrong.

Keep in mind that this assembly was removed from a used car, possibly with more miles than the car you have right now. There is always a chance that the replacement has the same problems or more.

This isn't supposed to be negative in nature - I just don't want you to perform a difficult service on your car when there are several easy and inexpensive fixes that combined take up less time than the swap will.

Regardless, let us know how it goes. Everyone deserves a working Haldex no matter the situation. Good luck, bud.
 
#26 ·
The Haldex came in yesterday but it was shipped to my Dad's dealership so I will be looking at it today after school. I kind of jumped the gun when ordering it since it came with a 6 month guarantee so if it did not work then it would not be a waste of money. I have a picture of the haldex and I think i can see some of the loom that would come from the controller but i am not 100% sure yet, and When you say controller, you mean the computer part of the haldex right? Or the haldex coupling itself. It definitely comes with the coupling lol and like i said, pretty sure it comes with the controller. When I first got the car, the ground strap was indeed broken, but was replaced, and that did not seem to fix it. But what makes me think that it is mechanically related such as clutch packs is the fact that it engages while off of the ground but I think when the weight of the car is put on the haldex, then it does not have enough strength to actually put power to the ground. It could be the clutch packs, or the stepping motor, Which are both more expensive than what i spent on the whole carrier assembly, and there is no guarantee that one of those are bad either. When I remove the old haldex from my car, then I will probably try to salvage it or sell it as is just to get some of my money back. I mean it has to be worth something right? I know that you guys are trying to help me, and I really appreciate that but I just want to get it DONE and working lol. Thanks again
 
#27 ·
Also, just to add I did the rollout test in the parking lot where you drive in a circle and rev it up. I remember doing it once and hearing a grinding/ rotating noise from the rear end. Not to mention, the car stopped in the same distance in both scenarios of the test.
 
#28 ·
Okay, quick update. After vacation I came back and switch to the proper matching rear tires. I now have 215/40/18s on the front and 245/35/18s on the back. The sizes are a perfect match in rolling diameter. As I expected, no difference in the Haldex, (I did not plan on having any difference anyway since it was broken). I recieved the Haldex Unit assembly and cleaned it up. It does come with the controller and everything I need to change it except that the plug is all messed up from when they removed it. I do not know if it is supposed to look like it does but it is just a connector with a bunch wires coming out of it. Anyway, I was wondering if it would be easier to just pull the haldex unit itself from the diff in the car and switch it with the new one. Would I need a new gasket for the haldex to differential if i did do that? I figured that if I just took off the haldex, I would not have to undo the axles and any other things. Also, what kind off differential fluid does the diff take, there was a rubber plug on top of the diff and it was shipped upside down so when I got it, the diff fluid had all leaked out. I am really excited to get this working, I just want to take the most logical route. What do you guys think? Thanks so much guys
 
#29 ·
Here's the issue: you need that connector to be intact to have any shot at a working Haldex.

These are the sorts of things that you need to be 100% sure of before you buy things from wreckers and salvage yards. Frequently they hack through wires and yank pieces apart that are crucial to the part's normal operation. You now will need to find the kit to replace/repair that connector as it insulates the controller connection from condensation/dust/dirt/oil/other debris.

Second - when you do get that connector fixed - the *more* logical approach at this point would be to swap out your controller and precharge pump with the ones that came with the unit you purchased. These jobs take very little time and will quickly eliminate the fixes that have already been suggested in this thread without you having to waste your time swapping out the entire differential and Haldex.

Provided that for some reason those swaps do not fix the issue, you could do the assembly swap if desired. There are good writeups on the TTForum and on the Vortex on the removal of the assembly. Generally, the idea is to remove the differential and Haldex as one piece as they are very difficult (if not impossible) to *properly* separate and reattach while still mounted on the car. If I remember correctly there are a couple one-time-use parts that need to be replaced. I will look around for a writeup and post one soon.

Most people recommend Redline synthetic oil for the diff in our cars. I would probably do the same if I were going to service it soon.
 
#30 ·
A broken plug makes it no good. Can a plug be replaced and repaired, sure but you do it incorrectly and introduce any sort of additional resistance to the circuit and it will not function properly. All along you said you are replacing the whole thing rather than do what we suggested and what you are suggesting now (meaning just trying the module before swapping all of it)
Anyway, instead of saying I told you so I'll help you. There is a "gasket" in there. It is like a metal crush gasket not a rubber one. I think its about $10 so get one before you start the job. Also get some fresh Haldex fluid and a filter so when you spill some while doing it you can replenish the fluid. I would tell you that you can just top it off a bit but the only way I know of putting fluid in the Haldex is through that bottom plug by injecting it up there so I cannot figure out how you would just add some when you pull out the plug it all leaks out. Also I never heard of anyone mentioning how you can check the level, I was always under the impression that the tube of fluid you buy is the amount that should be in there so drain it out and inject the new tube.
 
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