Slight "shunt" as clutch goes out

[Gyp]

My SM is the first 4x4 I've owned, so I don't know if what I'm experiencing is normal or not.

 

When I let the clutch out to move away from a stop, there seems to be a slight "shunt" in the transmission. It's as if the car momentarily slows, then takes up the slack in the transmission before moving off.

 

It seems more pronounced if I'm turning at the time, and doesn't seem to happen on any other gear change, just when I'm starting off.

 

Is this a normal characteristic of the four wheel drive system?

[nomdeplume]

Not in my experience with a 35k mile 4x4 Yeti. Sounds like you need to take it to your Skoda dealer for an investigation. Be sure to make sure that your dealings with them are well documented.

[armayeti]

That shouldn't happen. I've had my 4x4 Yeti for 3 years and never had any problems with the clutch in any gear.

[dbg400]

Contrary to the experience of the last two posters I've had this from new in my Yeti. Always a slight hesitancy just after moving off, particularly if turning at the same time (like when pulling out of a parking space). It's a little annoying, but is no worse (or better) than when I first noticed it 23K miles ago. There were quite a few posts saying similar when I got mine, so it's not an isolated issue. 

[weasley]

This has usually been put down to the Haldex shoving some drive to the rear wheels. Mine does it, always has.

[Gyp]

Not in my experience with a 35k mile 4x4 Yeti. Sounds like you need to take it to your Skoda dealer for an investigation. Be sure to make sure that your dealings with them are well documented.

 

Out of interest, which Yeti do you have?

[Yety]

"They all do that sir"

 

It's been discussed for ages on here from the start - no one knows what it is.

 

I'm sort of veering towards a Haldex conflict when wheels are rotating slowly at different speeds, ie on full lock in first gear that either tightens/relaxes the Haldex drive and/or the engine software to compensate. I don't know :think:

 

It only happens on fullish lock, from a standing start, hot or cold. One thing I can try tomorrow is on wet gravel as tyre slippage might be more than the normal tyre/road grip.

 

It's not annoying,or anything really wrong, just a quirk that is currently seemingly unexplained. The Haldex clutch is self powered by an electric pump rather than earlier versions that relied on wheel rotation to power the hydraulics, so a start up procedure/pressure build up can be ruled out.

 

ps: to add it's nothing to do with the clutch as it happens when the clutch is fully engaged and the car is moving off

Edited 2 April, 2014 by Yety

[Gyp]

Well, after the first two replies I'm rather more reassured.

I'm afraid my searches for shunt brought up accidents rather than this phenomenon, so I'm sorry if it's been discussed at length already.

[Ryeman]

Does it depend on the speed of your actions?. In the sense of time taken to depress clutch engage gear and re-engage clutch.

I'm thinking of the 'programmed' 2 sec hill-hold software.

Eg: boy racer v mr plod might show it up as a 'quirk' of the system that's part of the programme.

[nomdeplume]

Out of interest, which Yeti do you have?

140 HP diesel 4x4 top French spec LHD

[nomdeplume]

6 speed manual

[mrchrispy]

I get something similar, its only very slight and the wife doesnt even feel it when she drives but I can. 

When pulling away in 1st there is a ever so sensation of something happening with the rear wheels, like the rears kicking in.

clutch is full out and car well under way but I've never noticed if its when I'm turning, I'll have to check it out.

1st 4x4 i've drove to so I dont know ifs its normal or not.

 

Doesnt seem to be an issue.

 

Its a 140 4x4

Edited 3 April, 2014 by mrchrispy

[MajorTom]

I was wondering - in another thread on SuperPro poly bushes - whether this sensation was transmission shunt, or the engine and gearbox moving on its mountings as you engage the clutch. I find it a bit irritating.

[mrchrispy]

deffo rear in my case. engin is solid

[muddyboots]

I can add to the "mine does this too" list

 

Always notice it when pulling away from a standstill and turning. Time I always notice it, is when pulling out of a parking space in the works car park.

 

If my understanding of the Gen 4 Haldex is correct, it always engages the rears when pulling away from a standstill. So perhaps the shunt is when the rears disengage when it decides you're driving gently enough and traction at the front is OK. Maybe.

 

If anyone had the inclination, it should be possible to show it's the Haldex by pulling the relevant fuse and seeing if the shunt goes away...

 

Does the Off Road button leave the Haldex permanently engaged ? If so, and my theory is correct, the shunt shouldn't happen when I pull out of my parking space. Might try that and see what happens.

[Tech1e]

Just remember regardless of haldex operation you are still turning the angle box and the propshaft, I wouldnt be surprised if there was a little shunt from the driveline.

[muddyboots]

Just remember regardless of haldex operation you are still turning the angle box and the propshaft, I wouldnt be surprised if there was a little shunt from the driveline.

It happens during otherwise steady state though; I've pulled out of my parking space, clutch is already up, I'm steering on a constant lock, at a slow steady speed, and then you feel this gentle thump.

So I can't see what else would cause it other than a change in Haldex state.

[Guest]

Not sure if relevant, but I experienced this once on my Octy Scout; 'shunt' when pulling away, changing gear and accelerating. Read somewhere (possibly the Octy II section) it was due to the clutch plate getting wet. I had jet washed the car the night before, including using an angled lance under the engine bay.

It may be coincidental, but now I use a more gentle spray under the engine I have not experienced it again.

Fin

Sent from my GT-I9300 using Tapatalk

[MajorTom]

I'm not convinced about the Haldex explanation; there wasn't any thump with the Audi A4 (in the identical configuration) ie quattro 1.8T M6 that I tested. I think I'll source some stiffer engine and gearbox bushes.

[Huskoda]

I'm not convinced about the Haldex explanation; there wasn't any thump with the Audi A4 (in the identical configuration) ie quattro 1.8T M6 that I tested. I think I'll source some stiffer engine and gearbox bushes.

Audi A4s don't use Haldex as they have longitudinal engines. They have Torsen centre differentials.

 

My Octavia 4x4 sometimes made a clunk when setting off while steering a lot to one side.

[ejstubbs]

Mine has done this in the past - in fact I even started a thread about it back in July 2012.  If you check that out, you'll see that quite a few other people reported similar symptoms.

 

I have to say that I don't actually know whether it still does it.  Whether that's because it's stopped doing it or because I've just got used to it, I don't know!

 

If anyone had the inclination, it should be possible to show it's the Haldex by pulling the relevant fuse and seeing if the shunt goes away...

 

Hmm, interesting idea.  Might have a go at that. I wonder what warning lights it would trigger on the dash?

 

Oh, hang on...looks like it's fuse 22 on the dash panel, which also powers the instrument cluster - so maybe none, then!  The power steering runs off that fuse too, so taking it out might make the "pulling away on full lock" test a bit more of a wrestling match!

 

Does the Off Road button leave the Haldex permanently engaged?

 

If you mean does it maintain constant drive to the rear wheels. then no. I don't believe it does.

[Pouclee]

My old Yeti did it but the new visually impaired one doesn't, wonder whether it's the differences between Haldex 4 and 5.

[muddyboots]

Now I've read the self-study guide on the Haldex and how it connects to the gearbox etc, I have a theory for the "thump" issue...

 

A common theme seems to be that it happens when pulling away from a standstill AND steering at the same time.

I notice it when I'm pulling out of parking spaces.

 

This means there's a reasonable amount of steering angle.

 

When the car is moving like this, the path taken by the rear wheels will be of a smaller bend radius than the front wheels.

So the front wheels travel further and therefore rotate faster than the rears.

That means the crown wheels of the front and rear diffs will be turning at slightly different speeds.

 

However, the Gen 4 Haldex clutch apparently engages fully when pulling away from standstill, effectively locking front and rear diffs together.

 

So - 2 diffs locked together but trying to turn at different speeds - what gives ?

 

I noticed while under the car that the front and rear propshaft couplings are actually flexible - they look like they're made of some kind of rubber.

And of course the front transmission/engine, and rear drive unit will be on mounts with a little "give".

 

So I think when you pull away from standstill and are turning, some tension builds up in the drivetrain, and this is suddenly released with a thump when the Haldex clutch releases a little when it realises full engagement isn't required.

 

I think I'm also right in thinking that the Haldex clutch will disengage when braking is detected. 

If that applies to use of the handbrake - then just lifting the handbrake lever ever so slightly (so the warning light comes on - but no actual braking effect is applied) could be a way of forcing the Haldex to disengage and proving the theory - rather than trying to pull any fuses

[vegit8]

FWIW mine does the same pre F/L 140 4x4, as others have stated only on pull away and turning at the same time.

Definitely some sort of conflict between the front and rear axles.

[Gyp]

Now I've read the self-study guide on the Haldex and how it connects to the gearbox etc, I have a theory for the "thump" issue...

A common theme seems to be that it happens when pulling away from a standstill AND steering at the same time.

I notice it when I'm pulling out of parking spaces.

This means there's a reasonable amount of steering angle.

When the car is moving like this, the path taken by the rear wheels will be of a smaller bend radius than the front wheels.

So the front wheels travel further and therefore rotate faster than the rears.

That means the crown wheels of the front and rear diffs will be turning at slightly different speeds.

However, the Gen 4 Haldex clutch apparently engages fully when pulling away from standstill, effectively locking front and rear diffs together.

So - 2 diffs locked together but trying to turn at different speeds - what gives ?

I noticed while under the car that the front and rear propshaft couplings are actually flexible - they look like they're made of some kind of rubber.

And of course the front transmission/engine, and rear drive unit will be on mounts with a little "give".

So I think when you pull away from standstill and are turning, some tension builds up in the drivetrain, and this is suddenly released with a thump when the Haldex clutch releases a little when it realises full engagement isn't required.

I think I'm also right in thinking that the Haldex clutch will disengage when braking is detected.

If that applies to use of the handbrake - then just lifting the handbrake lever ever so slightly (so the warning light comes on - but no actual braking effect is applied) could be a way of forcing the Haldex to disengage and proving the theory - rather than trying to pull any fuses

Excellent. Makes perfect sense.