Shudder when slowing down

[Silver Caravelle]

Hi all,

Multivan TDI auto is experiencing a slight drivetrain shuddder/vibration when deaccelerating (i.e not braking - but costing) from time to time.

Seems to be more likely when fully warmed up and is more noticable from 3rd to 2nd gear and in the 1300 - 1200RPM rev range.

Any thoughts? Could it be something to do with torque converter lockup not unlocking/sticking?

Thanks,

Scott

[gregozedobe]

Could it be the DPF in the middle of a regeneration ?

[Silver Caravelle]

Could it be the DPF in the middle of a regeneration ?

Hi Gregozedobe,

Many thanks.

Can you please elaborate?

I know when DPF occurs, the engine runs rough (coupled with a Turbo gushing noise) during this process and tends to occur about every 500 to 700km.

The deacceleration shuddering/vibration is when the vehicle is slowing down as described. The engine is running smoothly.

Other thoughts I had, it might be a slight exhaust resonance (in a engine breaking sense) at certain exhaust temperatures, leaking some shuddering/vibration back through the chassis via the mounts...but not all the time. Alternatively something to do with the lock up torque convertor not disengaging at the correct revs and slow down speed.

Cheers,

Scott

[gregozedobe]

Sounds like you know about DPF regenerations and what they feel like without my assistance, so your vibration is probably not the DPF.

I only mentioned it because you said "from time to time" and some people aren't aware that their vans does a DPF regeneration every now and then (more or less often depending on driving conditions) and the regeneration does cause rough running and vibration which is much more noticeable at lower revs (at higher revs you tend to not notice it so much).

Maybe you could do a search over at the Brickyard and see if you find any likely causes (use advanced search with "any date") ?

http://www.brick-yard.co.uk/forum/t5...ums_cat12.html

I don't have too many other ideas for you except for this unlikely one (but it is cheap and not too difficult to try out):

To check for exhaust resonation you could temporarily put the exhaust under tension with a few bits bit of wire here and there and see if it had any affect (better or worse) on the vibration you are currently getting. If it makes a change then that might indicate the problem is in your exhaust (but will tell you nothing either way if it doesn't make any difference or creates a totally new vibration/noise).

If you do find out the cause please add to this thread

[Silver Caravelle]

Hi gregozedobe,

Thanks again for the response. Yeah I think I can now rule out the DPF.

Great idea regarding putting tension on the exhaust with wire to test this.

If I get to the bottom of it I will definately post the results.

Still wondering if it might be related to the torque converter not unlocking consistantly, causing a shudder on slow down.

Cheers, Scott

[gregozedobe]

Still wondering if it might be related to the torque converter not unlocking consistantly, causing a shudder on slow down.

I don't know a whole lot about how autos work (personally I think that all autos, DSGs etc are the work of the devil ) and torque converters/lock-up mechanisms specifically, but thinking out aloud (which might or might not be helpful, but hey, free advice is often quite variable in both quality and utility and no one else seems to pitching in to help so far ):

I thought the lock-up mechanism was similar to the clutch on a manual ie they are designed to be either locked up or released, and went from one state to the other fairly rapidly. To produce the bibration you are taliking about they would need to be either running partially locked up and "juddering", or locking and unlocking on a very rapid cycle.

I'd probably talk it to an auto gearbox specialist and get their opinion (IIRC there have been threads about auto gearboxes either here or on the brickyard a few times in the past).

[Silver Caravelle]

I don't know a whole lot about how autos work (personally I think that all autos, DSGs etc are the work of the devil ) and torque converters/lock-up mechanisms specifically, but thinking out aloud (which might or might not be helpful, but hey, free advice is often quite variable in both quality and utility and no one else seems to pitching in to help so far ):

I thought the lock-up mechanism was similar to the clutch on a manual ie they are designed to be either locked up or released, and went from one state to the other fairly rapidly. To produce the bibration you are taliking about they would need to be either running partially locked up and "juddering", or locking and unlocking on a very rapid cycle.

I'd probably talk it to an auto gearbox specialist and get their opinion (IIRC there have been threads about auto gearboxes either here or on the brickyard a few times in the past).

Many thanks for the further pointers.

I often trawl the Brickyard and T5/T4 forums, even the US TDI forum. Those poor buggers are preoccupied with their Duel Mass Flywheel issues on their manual vehicles

Cheers, Scott

[Silver Caravelle]

Hi all,

Thought I would give you an update of my absolute frustration at present with my Multivan. You may recall I have experienced some vibration/reasonance and shuddering for quite a while now.

I have returned from about 2500 km's of touring from Melb to Sydney to ACT and back. Well nothing has changed and what is evident is the drive train vibration/reasonance/buzz particuarly after a number of hours of driving, shuddering/vibration on overun (when coming to a slow standstill).

As an example, climbing up the steep hill on the HWY at Wollongong at say 80km in 5th or 6th it was horrible with lots of reasonance.

When revving in neutral there is a real harmonic vibration at 1800rpm that leaks through the chassis to the accelerator pedal. There is plenty of off idle harmonic vibration in the 1000 to 2000 rpm range.

I have check everything I can possibly get at. I don't believe it is exhaust, engine mounts etc. I can also hear a muffled tinny rattling sound from the transmission (but could be the alternator area??). There is 'hollow' sounding noise from the transmission sump with a lot of vibration felt when putting hand briefly on this with engine idling.

I am really hating driving this.

So I think it is off to the dealers again for another look after a few months of gauging the matter. The problem is that I do not think they will isolate the issue and tend to fob one off in any case saying it is within normal limits.

I starting to think it could be to do with the auto transmission flexplate or TC having attempted to rule out other things. But the auto still shifts ok and doesn't slip.

Any other thoughts or comments?

With thanks, Scott

[gregozedobe]

Hello Scott,

Sorry to hear you are still having problems.

What have you done to eliminate the exhaust as a possible cause ?

Resonation/vibrations can be very difficult to track down, as they often seem to originate a long way from the actual source. I had an annoying buzz in my T5 that seemed to be coming from the far left of the dash, but in fact it was caused by the interior light in the ceiling (the missus located it by moving her head around to different locations while I drove).

TDI engines are pretty rough at idle even when they are running correctly.

Sometimes something can be touching something it shouldn't be, and that can cause quite loud noises. Unfortunately it is a bit difficult to have a little person sitting in the engine compartment to push and hold various things while you drive along to find the real culprit.

Have you tried driving another T5 with the same engine and gearbox to see if they have a similar resonance ?

It might be worthwhile paying for a thorough assessment from a GOOD auto gearbox specialist.

Good luck with your quest.

{start rant}

My T5 is currently sulking in the garage ATM with a permanently lit up "Exhaust Gas Warning Lamp" (the yellow outline of an engine), it is also quite gutless until 1,800 rpm, when it takes off like you have just switched a "power" switch on (it used to start pulling properly at 1,400rpm and build power progressively from there).

The dealer is too busy to look at it until 22 Jan. This is the third time it has been undrivable due to engine problems (and that's not counting the myraid other smaller problems). If it wasn't so nice to drive it would be gone. At least I have another 3 years of VW extended warranty to rely on (and I suspect I'll need it).

I'll report back with the official diagnosis (and solution) when it gets fixed.

{end rant}

[Golf Loon]

What car is it Mr Caravelle? T4 or T5?

On a T4, I would check the rear engine mount on a hoist. The one behind the gearbox. They wear the rubber and get horrid vibration when slowing down.