Hello!

 

I'm having really interesting issue. Because I'm not mechanic I'll name it rear problem

 

Symptoms:

-1.- When I'm steering (doing corners) with applying throttle (gas) in 1st or 2nd gear, it seams that rear diff locks up as much it can. And sounds like something is the tearing apart. Only in 1st and 2nd gear.

-2.- This is very noticeable at the begging of driving. When I'm on the road lets say 10 or 15km, those symptoms are not so noticeable, but issue is still there,

-3.- When I'm not applying throttle, no issues.

-4.- When driving in straight line, no issues regardless of throttle applied or gear selection.

-5.- When reversing and steering same symptoms are like described in poin1.

 

Anyone with similar problems?

How did you solved it?

 

Many thanks for all answers.

Edited 5 December, 20241 yr by tetoon

Hi, what makes you think the rear diff locks? Do you have wheels slip, feel vibration or only sound?

 

These cars have open differentials, and slipping is only limited by brakes (Electronic LSD).

 

Cud be a cv joint, or a bearing in rear diff, or cud be anything else as well.

Hey hey.

 

Tnx for reply.

Welll.... at the end of spring some bearing sound appeared. Car had abt 200.000km. And we started with the less costly well bearings - rear wheel bearing. They were bad indeed. But the sound remained. So we proceeded with replacing diff bearings.

And we succeeded. After 10.000km described above problems appeared.

 

OBD data analyses shows that under condition (-1.- When I'm steering (doing corners) with applying throttle (gas) in 1st or 2nd gear, it seams that rear diff locks up as much it can. And sounds like something is the tearing apart. Only in 1st and 2nd gear.) that rear diff locks up to 34% which is max it can be achieved - according to VW mechanic's words.

 

Sounds are coming from rear part. I also talked with few guys, who are mechanics on trucks and transportation vehicles. Few of them were familiar with issues like described. Similar problem was spotted on VW Passat and VW Transporter 4Motion (Synchro). But unfortunately they don't recall the solution. I assume its not CV....

 

That's it. Don't know how to proceed further....

Tnx for all suggestions and sharing experiences.

Do you have different sized wheels or tyres on the front and rear axles?

Hmm there should not be any locking in the differential the car has, could the 'locking of differential' prefer to haldex clutches engagement then. The clutches cud slip but i have never heard this causing noises.. the power just does not reach rear..

 

Any locking would be brakes applied to left or right wheel. If that happens incorrectly because of some sensor it could cause the issue but i dont believe that is the case, just trying to think... That would most likely also cause other problems or DTCs.

 

I guess you changed rear diff fluid while doing the bearings, probably the haldex has also been serviced?

 

One cud easily assume cv joints dont give such problems but it might be worth checking. While cornering, accelerating and haldex fully engaged a single rear cv joint sees max torque it can and bad cv joints tend to show symptoms only under max load. Should happen around high torque rpm area of the engine. However they usually give some vibration too. 

 

Edit.

So you replaced bearings in the diff and problems started 10k km afterwards? 

Edited 5 December, 20241 yr by RattleWagon

The "locking" that has been described - "steering turned applying gas" will be transmission wind up not the differential planet gears locking up, there is a small degree of wind up or snatch present normally when reversing or driving forward on lock out of a parking space due to the pre-emptive engagement of the Haldex which I feel and am aware of but only because I drove proper 4x4's for many years.

 

Even when the Haldex is 100% engaged (I dont accept the 35% is maximum, that is nonsense, I have driven mine on test watching live data) it declutches momentarily every few seconds to release any transmission wind up. As I alluded to above different rolling diameters of tyres on front and rear axles will cause real problems of wind up.

 

I think the haldex plates are not releasing smoothly as they should, this could be a problem with the pressure relief valve, contaminated Haldex fluid or clutch plate metal contamination.

Of interest to me is where did you find the diff bearings and particularly the outer oil seals?

Just a horrible thought here.  Was the rear diff serviced recently or the Haldex serviced recently?  It is relatively easy to mix up the Haldex and rear diff refill holes and it is not unknown for the rear diff to fail due to Haldex oil being put in and vice versa.  See other threads on this:

 

Hello!

 

Tnx anyone for replying the topic. I appreciate!

 

On 05/12/2024 at 12:36, J.R. said:

Do you have different sized wheels or tyres on the front and rear axles?

No. The wheels/tires are all same size. In this moment winter M+S, 16". Stock size.

 

Quote

Hmm there should not be any locking in the differential the car has, could the 'locking of differential' prefer to haldex clutches engagement then. The clutches cud slip but i have never heard this causing noises.. the power just does not reach rear..

Any locking would be brakes applied to left or right wheel. If that happens incorrectly because of some sensor it could cause the issue but i dont believe that is the case, just trying to think... That would most likely also cause other problems or DTCs.

I guess you changed rear diff fluid while doing the bearings, probably the haldex has also been serviced?

 

The tearing or rattling sound is not so audible more felt when you are inside car. And yes; the hole thing its like driving, being in a proper off-road  vehicle or true quattro Haldex pump and oil was changed 1y ago.

 

Quote

One cud easily assume cv joints dont give such problems but it might be worth checking. While cornering, accelerating and haldex fully engaged a single rear cv joint sees max torque it can and bad cv joints tend to show symptoms only under max load. Should happen around high torque rpm area of the engine. However they usually give some vibration too. 

 

Accelerating in straight line is no problem. And also accelerating in 3rd and does not cause any issue.

Hi power, hi toque and 90° turns are usually made on intersecting roads, parking lots, country roads,etc And exactly this kind situations described issue occurs on paved surfaces only.

 

So.... you think/suggest that CV joint is worth of checking?

 

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So you replaced bearings in the diff and problems started 10k km afterwards? 

Approximately yes. All bearing in diff. Haldex remained unservicesed. Just oil change.

 

Quote

The "locking" that has been described - "steering turned applying gas" will be transmission wind up not the differential planet gears locking up, there is a small degree of wind up or snatch present normally when reversing or driving forward on lock out of a parking space due to the pre-emptive engagement of the Haldex which I feel and am aware of but only because I drove proper 4x4's for many years.

I can assume we are describing the same sensation, feelin - it feels like proper 4x4, or quattro. To much engaged.

 

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Even when the Haldex is 100% engaged (I dont accept the 35% is maximum, that is nonsense, I have driven mine on test watching live data) it declutches momentarily every few seconds to release any transmission wind up.

Yes. I talked with mechanic again and you are correct; he was describing me engaging the Haldex clucth and % so on

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As I alluded to above different rolling diameters of tyres on front and rear axles will cause real problems of wind up.

I think the haldex plates are not releasing smoothly as they should, this could be a problem with the pressure relief valve, contaminated Haldex fluid or clutch plate metal contamination.

As first step in solving problem, we decided to go with oil change.

Metal contamination? Like disintegration Maybe. We will see if oil replace would wash away

 

Quote

Of interest to me is where did you find the diff bearings and particularly the outer oil seals?

I can't answer that question. I was informed that spare parts are not available at all. And group of guys; found a solution of modifying Audi and SKF bearing and modifying bearing bed. Guys gained experiences in Skoda Service and modifying rally race cars.

Like I said; I'm not mechanic. I can only have faith that the did right job....

 

 

I'll give report after oil change. We will see.

 

Tnx again to all!

Kindly regards,

3 hours ago, tetoon said:

I can assume we are describing the same sensation, feelin - it feels like proper 4x4, or quattro. To much engaged.

 

Like an old school proper 4x4 without a central differential, I think the Quattro had a central diff, my Sierra XR4x4's all did.

 

You are describing transmission wind up and then the snatch when the Haldex clutch releases, I feel it driving away from a car parking space on full lock, I understand what it is and it doesn't concern me. TBH the majority of drivers would be completely unaware, if you have mechanical sympathy and are in touch with your vehicle then the sensation is disturbing.

 

If you are feeling it during normal driving at small steering inputs then something is amiss, you can view the commanded Haldex engagement in real time using the datalogging function, if it feels like there is more engagement than is commanded then you need to start looking at the hydraulic pressures, I think they can also be viewed, if it is snatching when the live date shows the clutch pack being released and the pressure dropping then its probably mechanical/contamination, maybe the wrong preload.

 

The action of the multi-plate wet clutch should be very smooth, I have never known a fierce wet clutch but as I said my car does exhibit the symptom but in conditions when I know there will be considerable transmission wind up, the Guibo coupling will be acting as an energy store.

26 minutes ago, J.R. said:

Like an old school proper 4x4 without a central differential, I think the Quattro had a central diff

Correct, the Quattro (note the upper case Q) had a Torsen centre diff - as did the early A4, A6, etc quattro (not the lower case q) versions. Later A4, A6, etc.versions switched to Haldex to lower emissions.

Edited 6 December, 20241 yr by PetrolDave

Hello!

 

Topic update:

After discussing with mechanic past week we decided to start solving problem step by step. First was Haldex oil change. And after 200km its promising. All symptoms was gone. So far, so good. Maybe some metal debris were present.

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You are describing transmission wind up and then the snatch when the Haldex clutch releases, I feel it driving away from a car parking space on full lock, I understand what it is and it doesn't concern me. TBH the majority of drivers would be completely unaware, if you have mechanical sympathy and are in touch with your vehicle then the sensation is disturbing.

Off course I take care of machine I just wanted to know if this symptoms can result in catastrophic failure and further expenses

 

Thanks to all for now. I hope I'll not have to write for help again near time soon

 

Kindly regards.

5 hours ago, tetoon said:

Maybe some metal debris were present.

Eyks - that's never good.  Was there a test to see if the pump was still good (i.e. did somebody test out the clutch engagement solinoid on the HALDEX gearbox) before handing it back to you? 

6 hours ago, tetoon said:

First was Haldex oil change. And after 200km its promising. All symptoms was gone. So far, so good. Maybe some metal debris were present.

Did you also clean the Haldex filter? That would have shown/collected any debris.

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Eyks - that's never good.  Was there a test to see if the pump was still good (i.e. did somebody test out the clutch engagement solinoid on the HALDEX gearbox) before handing it back to you?

Yea. Not good. No bench testing was made. And pump is supposed to be OK - its about 12-17 months old.

 

Quote

Did you also clean the Haldex filter? That would have shown/collected any debris.

No sludge was found on filter, but some metal dust/debris. Oil was replaced about 24 months ago and now again.

We will see. Now it's seems to work...