Superb 4x4 vibration when towing caravan

[SEman]

I have a 64 reg 170PS DSG 4x4 which has done 45000 miles. I bought it in March 2017 with 25000 miles on the clock, as the second owner and it has a full service history. I tow a 1300kg caravan and the car has performed very well. At its last service in February 2019 the diagnostics picked ups problem with the Haldex. Further diagnosis showed the haldex pump to be faulty. A new pump was fitted in April 2019 and the haldex fluid renewed. It has had an earlier   Haldex  fluid change whilst I have had it. 

 

Since the car has had the new haldex pump I can't say that i have noticed any significant difference in its sol driving characteristics. However last week when I towed the caravan since the pump had been replaced I noticed a thrumming vibration but only under certain driving conditions. If I was doing 50 mph on the flat and accelerated to 60mph then i felt a vibration cut in which ceased when the power demand on the car reduced. Similarly when coming to a slope say at 55-60mph the thrumming vibration would start but stop once the slope eased off. The car had the load equivalent of four 75kg adult inclusive of myself, wife, dogs and luggage. The caravan noseweight was 70kg include in the loaded weight.  Tyre pressures were 280kpi rears, and 240kpi fronts.  Tyre size 225/45/17 Michelin Cross Climates.

 

Yesterday taking the caravan back to storage I accelerated from 30mph to 50 mph on a flat A road and no thrumming vibration.  Tyre pressures 220kpa front 225 spa rear and with car unloaded.

 

The previous services had been in September 2017 and June 2018 and neither showed any fault on the diagnostics and when towing the car was just as quiet solo as when towing apart from some increase in engine noise under towing  load accelerating or on hills. Certainly the 4 wd system was working okay in September 2017 as I had to exit wet grass field with the caravan in tow and it all worked fine.

 

I have taken the car to the garage that replaced the haldex pump and they carried out a diagnostic and it came back okay.

 

Any thoughts on what might be causing the thrumming vibration would be welcomed.

Edited 25 May, 2019 by SEman

[vborovic]

Wheel (mis)alignment maybe?

[silver1011]

The additional weight of the passengers as well as the caravan will expose any potential weaknesses or wear in the transmission.

 

A thrumming on acceleration could be indication of some early signs of wear/play of the dual mass flywheel (DMF).

 

On manual gearboxes it is possible to minimise the strain being put on the DMF by maintaining a lower gear and higher engine speeds. This isn't as easy on the DSG, it will still be prioritising fuel economy over component longevity so holding higher gears for longer. This isn't necessarily good for the DMF.

[SEman]

Thanks for the replies. After the bank holiday I will be taking the car for a four wheel alignment check. When it happened I dropped it into Sport mode which increased the revs and seemed to reduce it somewhat, but it was still noticeably there. I guess I could have put it into Manual mode. But even when it was in normal auto mode the engine was dropping to 5 or 4 gear so it wasn’t labouring at low revs. 

 

I should clarify there there were only two of us in the car with dogs and luggage and noseweight. So I calculated that as being equivalent to a driver and three passengers plus of course the caravan hanging off the back. 

 

 

Edited 26 May, 2019 by SEman

[Ootohere]

@SEman

The Haldex was dealt with but  has the rear differential had the oil changed?

[SEman]

I’ve been back through the service records and none show a diff oil change. The Haldex was done at 30k by my garage, and again recently after having the pump replaced. The DSG oil was changed on its fourth annual service in June 2014. 

[3T51704x4]

Take the fuse out for the Haldex and retry.

When driving mine for a few weeks with the pump inop it seemed to be smoother, now with the new pump, there is a definite increase in drive train noise like you suggest which I suppose would be worse if heavily loaded ie towing a caravan. I did the pump filter Haldex oil and diff oil so don't waste money as it prob won't fix it.

Mine has done similar mileage but pre-facelift, my A6 Allroad also did this but as you know it torsen diff system not Haldex which suggests possible prop shaft damper or prop bearing issue.

When I bought mine, the previous owner had the clutch removed as he was advised the rattle over bumps came from the release bearing so they may not have put my prop back in the same location from the factory which can cause this sort of issue (the rattle turned out to be due to the fitting of Mickey Mouse brake pads which rattled in the calipers).

[SEman]

Thanks your experience sounds similar to mine. Solo the car drives smoothly with little drive train noise. I had thought of removing the Haldex fuse next time I tow to see what the effect is. The Haldex oil was renewed when the new pump was fitted. With other commitments I’m unlikely to tow in the next couple of months but will be having a wheel balance and alignment check soon. 

[silver1011]

On 26/05/2019 at 18:00, SEman said:

When it happened I dropped it into Sport mode which increased the revs and seemed to reduce it somewhat...

 

Another nod towards a grumbling DMF.

[SEman]

Oh cheers, the dreaded DMF the curse of the diesel as well as DPF -)

[TheRobinK]

Not all Superb Diesels are cursed with one - the 1.6 CR's don't have a DMF.  

 

That said, they don't have your 170 horses or 4x4 capability either ...!  

 

 

[SEman]

I thought that i would post an update since I have towed the caravan some 600 miles during August. Solo the car has started to show the vibration when under some load like going up hill, but even then the vibration can only be induced by giving it some accelerator from around 45-50 mph and taking it up to over 60mph. It seems to come in around 2000 revs in 5th gear. The service manager at my local independent VW/audi specialist got i to do it, but it was over so quickly that he couldn't with any confidence diagnose  anything. They put the car up on the ramps and gave the underside a good inspection but couldn't find annoying untoward. I have had the wheels aligned and it made no difference.

 

Towing the caravan does get the vibration to happen more frequently but mostly on inclines as on the level it disappears unless I accelerate with the caravan in tow. Solo the car seems to be more "boomy" at lower revs. 

 

So that's about it thus far. For information when DMF does fail is it rapid and likely to do damage, or is it likely to be more gradual so that you can pull over, or as it worsens take it to a garage.

[SuperbTWM]

Do you have any vibrations at idle?

[SEman]

Not that I’ve noticed. When the vibration does occur I’ve touched the gear lever but it’s dead steady. Where might be the best place to feel for vibration on tickover?

[Ootohere]

@SEman 

Reading your OP,  do you have a tyre inflation device or pressure gauge that gives you the kpi rather than just psi or bar?

[SEman]

Yes my digital gauge can read koi, bar and psi. I use the kpi scale and cross check it with a Schraeder pencil gauge and a mechanical gauge too. 

[allenbrown21]

There are several reasons for this issue, you have to analyse where is the vibration coming form few reasons can be: the over load issue, properly not balance the towing hitch with caravan, some things is vibrating while driving etc. do one thing try to change you truck and drive with other truck and check is that still vibrating or not you will got to know where is the problem, I had a Ram 1500 truck when i overload the stuff on that then its makes some vibration, i used that for towing roadside assistance nyc, now i am using supper heavy duty truck from Ram 6500 diesel engine.

[SEman]

The car and caravan are always loaded in a similar manner with the nose weight at between 70-80kg and the car is certainly not overloaded. The car does exhibit the vibration when solo so it’s not just when towing. I’m coming to the view it’s the DMF on its way out. So I’m just driving it sensibly and keeping watch on it. 

 

Anyway the vibration is a second order problem as I’ve just had to drive 80 miles home with the ABS and ASC orange lights and a red warning all illuminated. And I thought these were reliable cars! 

[Gmac983]

If you can hear the dmf rumbling on idle things have gotten really bad! Prolonged use of the car with a failing dmf can be catastrophic for the engines bottom end bearings due to the excessive vibrations. Had several transit vans/trucks at work that needed engine changes because of it. (although to be fair the vans had been run way past the point of when the dmf should have been change and the particular age group of transit were notorious for the problem). 

 

Having said that your vibration/noise could be the prop shaft damper failing. I had one fail on my A3 Quattro a few years back. The vibration was only there under medium to hard acceleration. Cruising it was just fine. 

 

45k seems rather low mileage for a dmf to fail. Has the car done a lot of towing miles? 

Edited 19 September, 2019 by Gmac983

[WesH]

Did anyone get to the bottom of this?? I have a similar problem. 

My 2012 cr170 4x4 does exactly the same, but only since transferbox issues, bought a good used box and prop (old one damaged when transfer shat itself).

Pull the haldex fuse and drives perfect. 

Any advice appreciated.