Haldex failure symptoms... Need advice

[The Fed]

Thanks all!

So on my way home I took a side road I know has a few open gravel areas to test it out. I launched the car hard while watching the rear wheel via the side mirror set at an angle I could see the whole rear wheel.

Sure enough, front wheels spin away while the rear just rolled at the pace of the car (like 5 mph). The rear end of the car is clearly not getting any power. It also made a bit of noise that came from the vicinity of the rear diff. Like maybe things slipping that shouldn't be....

So off to the dealer. Thankfully the car is box stock, and under warranty.

Nestor = I crawled under my car and took a pick of the bottom of the diff with my phone. It is just behind where the driveshaft meets the diff (Icould reach it with my arm no problem). There is 9 digit code that is cast into the diff housing/case. Then there is a 10th digit (a letter) that is molded next to the cast numbers. Here is a pic...

Thanks again for the quick replies. I will follow up just in case anyone is interested.

Cheers!

josh

GRAVEL??!!

 

[The Fed]

Get someone to take a video of the front wheels "smoking". I can't believe there's no codes that are set for this condition. Were there any messages in the Infotainment or idiot lights on the dash when this happened?

 

[davewg]

Try a different dealer?

 

[josh_]

Yo!

So here is the VW tech's notes. This is Dorito Bros VW in Walnut Creek, CA;

If anyone has any insight I would much appreciate your thoughts...

I am going to re-test, and bring a buddy to film my results. I will let y'all know how it goes....

Cheers!

josh

 

[SweetJones_29]

What do you want them to do if the issue does not present itself when you are at the dealer? If it happens once there is a good chance it will happen again. Unfortunately it will take up some of your time but if there is a problem it will get fixed.

 

[josh_]

What do you want them to do if the issue does not present itself when you are at the dealer? If it happens once there is a good chance it will happen again. Unfortunately it will take up some of your time but if there is a problem it will get fixed.

They did what they are supposed to do. And I will take it back when it happens again. I do wish they had tested the pump or at least took a look at it....

But oh well. Again. I will test it again. If it throws a code, take it back and hope the next step happens. I get the algorithms. I just wish it was easier to prove....

Cheers!

josh

Sent from my Pixel 2 using Tapatalk

 

[josh_]

Just a quick update...

Took the car back in a week after they cleared the code. It was raining again that week, and the awd was clearly not working. All the usual symptoms. I dropped the car off on a rainy day, and they were able to replicate I guess. I had mentioned that possibly it was a good time to change the Haldex fluid (car was about 28k mi last week) and possibly inspect the pump at the same time. They followed my lead, and ended up replacing the pump, fluid, etc. and then claimed the car drove great and was all fixed! Sweet! Until I got the car back and had the same issues as before. Fail.

The good news is the horrid cavitation noise it was making is gone. So it sounds like the pump was clogged or not getting the proper amount of fluid BEFORE the pump replacement (speculation on my part). But when I was driving home from the dealer, I had to stop on a very steep incline before I turned left at a stop light. Light turns green, and car practically stood still as the RPMS built. Clearly awd is not working. So back to the dealer this week. I got some sort of nut ballz flu this week, so I have been laid up for days recovering. I hope tomorrow to get an apt. at my dealer and see what else they can find.

My guess at this point is the failure goes something like this....

1. Pump clogs/fails causing weak or no clamping force on the rear diff clutch plates when rquested.
2. Clutch plates torch themselves just like a poorly engaging DRIVE clutch, destroying the clutches even further (just like a slipping drive clutch that is old, etc. I picture a new driver slipping the clutch poorly, high rpms, lots of burnt clutch smell, etc).
3. VW dealer goes through process, replacing the pump first. Clutch packs are now getting proper clamping force, but clutch packs are fried, so it doesn't matter if the system is working. New clutch packs/rear diff needed.

I know that is petty simplified, but it seems to make sense. VW also replaces the Haldex control module in many cases, as I believe there was a bad version early in the build process.

Soooo, off to the dealer again to see what they can do. A bummer really because I ADORE this car. When awd works. I am a bit worried moving forward that will happen AGAIN in 20k miles. Lets hope not!

Cheers!

josh

 

[NCM]

My guess at this point is the failure goes something like this....

1. Pump clogs/fails causing weak or no clamping force on the rear diff clutch plates when rquested.
2. Clutch plates torch themselves just like a poorly engaging DRIVE clutch, destroying the clutches even further (just like a slipping drive clutch that is old, etc. I picture a new driver slipping the clutch poorly, high rpms, lots of burnt clutch smell, etc).
3. VW dealer goes through process, replacing the pump first. Clutch packs are now getting proper clamping force, but clutch packs are fried, so it doesn't matter if the system is working. New clutch packs/rear diff needed.

I know that is petty simplified, but it seems to make sense.

I'm betting you're dead right about the sequence of events. You'd think that weak oil pressure to the clutch actuator would throw a fault code, but maybe not?

Neil

 

[josh_]

Update for those who care....

Dealer replaced the entire rear end. Same outcome as many of the other folks who had this issue. Some important notes;

1. The notes state the tech "tested" the awd and it "appears" to be working fine.
2. The tech noted the Haldex pump had been replaced (same tech who replaced it FWIW), and decided to inspect the fluid that was changed 2 weeks ago.
3. Said tech finds "metal shavings and bits" in the just changed fluid.
4. VWoA techs give the OK to replace whole unit.
5. I received the newer "L" version of the rear end.

I have had the car a week now since the repair and all is well. I tested it in the same places, and it is clear at this point that the AWD is working well. The car feels different and corners MUCH better in sketchy situations. I am not able to get the traction control to come on when accelerating. I am pretty happy with the outcome.

My only reservation is when to change the Haldex fluid/pump in the future. Mine made it to 25k mi, and I very much hope this new diff has been revised in that it will last much longer. But I am almost ready to change the Haldex fluid when I change the oil. I am still betting the clogged pump was the original issue that caused the rest to fail. Anyone else have thoughts on this?

Anyway, I am super stoked to have my car working again! Thanks for the help and support!

josh

 

[Urlik]

What is your theory on how a clogged pump would ultimately result in metal shavings in the oil? Seems more likely that it would be something else failing and the resulting shavings would clog the pump.

 

[NCM]

My only reservation is when to change the Haldex fluid/pump in the future.

I'd probably want to check the Haldex pump's filter screen pretty early, at maybe 10 or 15K miles, and then use whatever you find as guidance for a future service interval. While checking the screen does require draining the Haldex oil, it's still a cheap enough procedure.

Neil

 

[josh_]

What is your theory on how a clogged pump would ultimately result in metal shavings in the oil? Seems more likely that it would be something else failing and the resulting shavings would clog the pump.

Here it is;

I believe at some point after 10k miles, the early build Haldex diff's maybe had bad clutch packs (or bad something...). As the "bad" clutch packs fail, the material they let go gets backed up/clogged on the Haldex pump's "filter". The filter clogs, fluid can't get past the clog, and the pump then fails to provide enough force to clamp the clutch plates resulting in MORE clutch slippage (think new clutch driver over revving, awful burning clutch smell, etc). Which results in MORE material being shed into the fluid.

I found a few articles with pics of folks who removed their pumps to find them pretty much completely blocked off at the filter. My rear diff made a nasty cavitation noise when I was testing the AWD before they replaced the pump. I believe that noise was the pump cavitating away due to the super clogged filter. After they replaced the pump, the noise went away. The pump is now working but the clutch packs are burnt toast. And my guess, outta spec (so far outta spec, not even an adaptation can make up for the lost material on the clamping surface). Although we have the proper pump pressure, the clutch packs are to thin, continue to burn up, hence the metal pieces the tech found in my fresh Haldex fluid.

Who knows if I am right or even in the ballpark with my assumptions. I am just super glad I was able to get it replaced under warranty.

Cheers!

josh

 

[josh_]

I'd probably want to check the Haldex pump's filter screen pretty early, at maybe 10 or 15K miles, and then use whatever you find as guidance for a future service interval. While checking the screen does require draining the Haldex oil, it's still a cheap enough procedure.

Neil

Thanks Neil,

I totally agree. I was thinking 10k as well. I have read the procedure and it is a very easy job in the garage. As you stated, cheap insurance so the unit doesn't eat itself again.

Cheers!

josh

 

[RoyB2]

I dropped my car off for oil change last week. Asked if there were any recalls or TSB on haldex/trans for my car (2015). They said nothing popped up on the computer. I need to get under the car and see what the number for mine is. I only have 12K miles.

 

[zhanghua92]

Thanks Neil,

I totally agree. I was thinking 10k as well. I have read the procedure and it is a very easy job in the garage. As you stated, cheap insurance so the unit doesn't eat itself again.

Cheers!

josh

any update with your car?