T6 4Motion differential catastrophic failure

[StevenD]

Hello,

I'm in trouble with my T6 and as far as I can tell it's a fairly unique problem. Any advice or insight would be greatly appreciated.

~4 Months ago I bought a lovely 2018 T6 Camper (converted), bi-turbo, 7 Speed DSG and 4Motion with 70k miles / 115km on the clock. I got it serviced as the timing belt was due, as well as new fluid in the DSG box and diff. This was at a mainline dealer here in Dublin so it wasn't a cheap service but I intended to keep the van for a long time. They said the flywheel was starting to go so I took it back to where I bought it and they kindly fitted a new one. Not the best start but ok so far.

Fast forward 2000km later and while driving down the motorway the rear differential exploded. I mean literally exploded, the housing is ripped in two (see picture), it tore itself off it's mount and where the drive shaft goes into the unit the housing is twisted about 1/4 revolution. There's also grease all over the sway bar just in front of the diff. I'll attach more photos tomorrow when there is some light.



There was a loud bang and a pretty violent jerk when it happened. We pulled in thinking it was a flat tire (or multiple flat tires given the noise) and the rear underside of the van was drenched in oil. We were just leaving a tollbooth and had the van just back up to speed when it happened. Didn't tear away or anything, just gently back up to speed. Nothing on the road either that could have hit it. I'm glad we were going in a straight line and not in the middle of a bend as the rear wheels locked up momentarily.

Has anyone come across anything like this before? The twist is I never asked the dealership for a diff service. I wanted the fluid in the Haldex clutch changed but that got mis-translated as a diff service. I only realised the mistake after this accident by looking at the part numbers on the docket for the service. I have read a few reports of Haldex fluid being mistakingly added to a diff and the diff going bang ~1000 miles later which seems very similar, but the back of the van is covered in gear oil. Granted I have no idea what Haldex fluid is like but it looks like the diff has the correct oil in it from the part number in the docket.

The van is sat at home for now. I got a preliminary quote for a new diff from VW but it's obviously silly money, 7k just for the diff and labour never mind whatever else is broken. Is it possible to delete the 4Motion diff and convert to 2WD?

Any insight / advice would be greatly appreciated. Thanks for reading.

 

[StevenD]

Some more photos to show the carnage:
The diff ripped off it's mount below.


Bottom of the diff


Input shaft

 

[DaveD]

Some more photos to show the carnage:
The diff ripped off it's mount below.
View attachment 173946

Bottom of the diff
View attachment 173947

Input shaft
View attachment 173948

Does your van have a differential lock?
The only thing that I can think of that could generate those forces would be a locked differential on a high traction surface.

 

[StevenD]

Hey Dave, thanks for replying.

That was my thought too, it's as if the diff locked up completely. It doesn't have a diff lock, there is no such control in the cab and the specifications for the van I pulled from the erWin portal state "Without mechanical rear axle differential lock". We were also going in a straight line so if a diff lock did engage it shouldn't have resulted in this.

 

[DXX]

I have read a few reports of Haldex fluid being mistakingly added to a diff and the diff going bang ~1000 miles later which seems very similar, but the back of the van is covered in gear oil. Granted I have no idea what Haldex fluid is like but it looks like the diff has the correct oil in it from the part number in the docket.

If you think incorrect oil was used during servicing try and salvage some oil from the casing and get an oil analysis report stating that you are interested in the oil type.
That said it would be hard to get a garage to admit to using the wrong oil.

 

[Loz]

I think VW would be worried to see this, get it to the main dealer and play on the whole safety issue and press for VW to cover this, especially as you have maintained it maliciously!

 

[StevenD]

Thanks for the replies.

I've taken what oil I could as a sample but from looking at the part number and quantity on the docket it looks like the correct oil was used. I'll look at getting it analysed but as you say it would be hard to get them to admit fault. They've already told me the service was done correctly. What I'm debating now is to send it back to them or get another garage to look at it. Again it would be very hard for them to prove a mistake, it's a pretty simple service.

I rang the importer and as it's out of warranty they have no real interest. The only option is to contact VW in Germany but as no one was hurt I can't see them taking much interest from a safety point of view. That is how I will approach it anyway.

From ringing around multiple garages / gear box specialists this seems to be unheard of. 4Motion isn't something you see much of in Ireland so that could be part of the reason.

 

[DaveD]

On reflection I'm now finding it hard to see how even if the wrong type of oil was used, it would cause such a catastrophic failure of the casting and mounting point. I'd be interested to see the internal bearings when it is removed.
Alternatively, is it possible that some muppet has used the bottom of the diff as a jacking point, causing stress fractures which later gave up?

 

[StevenD]

Something must have come apart inside it. There was no warning, no drone like a bearing going bad but it's buried at the back of the van so maybe I never heard it.

It's been up on the lift three times at the dealer for a gear box oil change, again for the diff (didn't have the correct oil when doing the gearbox) and again for a recent oil change with a visual inspection each time. They never noticed any cracks in the diff. I know it's hard to see a hairline crack without looking hard for one, but they did notice the flywheel was starting to go and it was only putting out the faintest sound so they seem switched on.

 

[T6ChrisO]

I have no constructive input as lack of mechanical knowledge but just wanted to say I hope you manage to get it sorted and not at your expense. Fingers crossed for the best outcome for you.

 

[yeha]

Looks like the pinion has stopped going round. The crownwheel has carried on rotating and pushed the pinion downwards.
I bought a T6 diff for £200. Pity you're over the water. I'd be interested in what's left.

 

[yeha]

Have to say, having looked at the pictures again, that's a very dry diff. I would expect a lot more oil especially on the fresh metal at the crack.

 

[Mud Digger]

Have to say, having looked at the pictures again, that's a very dry diff. I would expect a lot more oil especially on the fresh metal at the crack.

sorry no help but you would think oil would go every where at speed when it failed the casting broken edges are completly dry could this be due to a small oil leak from the service... but good luck hope you can get it resoved or fixed cheaply

 

[Paynewright]

I wonder if they forgot to refill it ? The cracked edges look dry?

I wonder if it is worth a transmission specialist looking at it - lack of oil would show in overheating bearings and gears.

 

[Salty Spuds]

I wonder if they forgot to refill it ? The cracked edges look dry?

I wonder if it is worth a transmission specialist looking at it - lack of oil would show in overheating bearings and gears.

Maybe someone didn’t put the filler plug back in or tighten it up.

 

[Robert]

I got it serviced as the timing belt was due, as well as new fluid in the DSG box and diff. This was at a mainline dealer here in Dublin so it wasn't a cheap service but I intended to keep the van for a long time. They said the flywheel was starting to go so I took it back to where I bought it and they kindly fitted a new one.
...
The twist is I never asked the dealership for a diff service. I wanted the fluid in the Haldex clutch changed but that got mis-translated as a diff service. I only realised the mistake after this accident by looking at the part numbers on the docket for the service.

Let me guess, was it Frank Keane VW in Liffey Valley?

 

[Loz]

Maybe someone didn’t put the filler plug back in or tighten it up.

That would be easy to check for..

 

[StevenD]

Thanks again for all the replies.

@yeha can I ask where you got a diff for 200 pounds? I'm guessing a breakers.

There was oil in the diff for sure, the back of the van was covered in it, and the road looked like it too although I didn't walk back up the motorway to look closely. There is a 1/2 inch gash all along the bottom of the diff so any oil that was in there has drained out. It would be very hard to prove they under filled it. The idea of getting a specialist to look at is a good one, they would probably recognise overheating. Whether that would be enough to prove a lack of oil is another thing.
I do monitor all my temps driving along but I don't record them (I mostly look at transmission temp because of previous issues with older cars). I'll pay closer attention in future as I _think_ I noticed a temperature increase after the service but still seemed well within limits.

The more I think about it the more I think they bungled the service. I can't find any any reports of these units going bad. I rang a lot of garages and specialists yesterday and none of them had ever seen anything like it.

 

[Loz]

Thanks again for all the replies.

@yeha can I ask where you got a diff for 200 pounds? I'm guessing a breakers.

There was oil in the diff for sure, the back of the van was covered in it, and the road looked like it too although I didn't walk back up the motorway to look closely. There is a 1/2 inch gash all along the bottom of the diff so any oil that was in there has drained out. It would be very hard to prove they under filled it. The idea of getting a specialist to look at is a good one, they would probably recognise overheating. Whether that would be enough to prove a lack of oil is another thing.
I do monitor all my temps driving along but I don't record them (I mostly look at transmission temp because of previous issues with older cars). I'll pay closer attention in future as I _think_ I noticed a temperature increase after the service but still seemed well within limits.

The more I think about it the more I think they bungled the service. I can't find any any reports of these units going bad. I rang a lot of garages and specialists yesterday and none of them had ever seen anything like it.

As suggested, did you check if the drain plug is still in place, as that falling out would also leave the oil all over the back of the van before the diff fails.

 

[StevenD]

Looking at the diff there doesn't seem to be a drain plug, only a fill plug. I guess to drain it you have to open it? The fill plug is tight anyway.

The manual I found on erWin also doesn’t show any sort of drain plug for the diff, nor instructions for draining it. There are only steps for checking the level and filling it.