Technical Clonk and bump at small speed.

[tomdee]

Hello dear Fiat users, recently my panda cross 4x4 1.3 Multijet started to make a clonk noise and bump that can be felt even in the gear lever. This only happens at low speed (1st and 2nd gear) and also with the engine in neutral or clutch pressed. It happens when going straight or turning and it is very evident when driving at low speed in the mall parking lot, for example.
The mechanic can't identify the origin and says it could be the gearbox or the transmission axles and wanted to rule out the problem by testing with a used transmission, unfortunately it's hard to find for this specific model.
Has anyone gone through something like this?
The engine was new and it has 40K kilometers without any problems (I have another thread about it here), the panda has 146K kilometers in total.

 

[Jiffycom]

If it happens when the car is out of gear then I can't see it being the gearbox. Does it clonk once or does it clonk clonk clonk, etc?

 

[tomdee]

If it happens when the car is out of gear then I can't see it being the gearbox. Does it clonk once or does it clonk clonk clonk, etc?

I goes "clonk", "clonk", "clonk"...
It only stops when there is some force on the accelerator pedal (car is in gear) and I increase speed.

 

[Jiffycom]

If the speed of the clonking increases with the speed of the vehicle then it does point to something related to the rotation of the wheels. My methodology here would be to work from the outside in. Check there's no major defect in the wheels or tyres then give the brakes a good inspection. After that, I'd be looking at the driveshafts and propshaft.

 

[tomdee]

The clonk goes away the minute you speed up to about + 20km/h

 

[Panda IIs]

The clonk goes away the minute you speed up to about + 20km/h

The reality maybe that it reaches a frequency (speeds up) to the point you cannot discern it.

Reading that it remains when the clutch pedal is depressed suggests it is on the drive line side of things (so perhaps not a clutch or flywheel issue - does MJ have dual mass flywheel, DMF?). Possibly a c.v. joint on the drive shaft(s) does driving around a corner (or in circles in the mall parking) make it worse?

 

[Jiffycom]

Driving in tight circles is a good test of CV joints. Does it make the noise in reverse?

 

[tomdee]

Didn't test it in reverse yet, but I don't see any difference wether I'm driving in straight or turning.

 

[Herts Hillhopper]

Take a look at the bearing and Universal joint half way along the propshaft to the rear wheels. A common failure on 4x4 models when the rubber ‘doughnut’ that supports that centre bearing breaks down through old age. The bearing is available separately but easier to replace whole shaft, now available from various sources at around £250

 

[tomdee]

So, I looked under the car, but as it is parked on the street I was not able to detected anything stranger other than the rust is a specific part of the propshaft for the rear wheels, just before the middle joint. I made a small video (terrible focus and steadyness) just to play and pause to try to see better.

VID_20220629_194233.mp4

Shared with Dropbox

www.dropbox.com

 

[The Panda Nut]

That prop shaft looks to have a split / cracked weld visible at the start of the video?

 

[Herts Hillhopper]

Looking at this, it doesn't seem too bad, and so I doubt that's causing the noise. In time, the rubber ring becomes two parts as it fails -- one fixed to the outer frame and one that sits round the bearing on the propshaft. Yours has what might be a tiny amount of cracking - arrowed - but still seems sound otherwise, and is better than mine. (Still 1 - but labelled 2.jpg!)
@The Panda Nut asks if there's a split weld - don't think so, just a shadow. (Still 2 - image 1.jpg). Mine looks the same.

 

[Herts Hillhopper]

Here’s mine, on a 2018 car at nearing 38,000 miles, with a bit more cracking on the rubber part… and a photo of a brand new support for comparison (I bought the centre bearing for a 2005 4x4 then discovered I had no chance of fitting it! Sold the car instead, although not because of this)

 

[tomdee]

Thank you all.
Next week will give it a proper look in the propshaft joint again, I'me currently driving with the company car so only have to time to check on panda again next week.

 

[tomdee]

So, been out on vacation and left the panda at the mechanic shop today. I told him about the mid transmission shaft bearing so that he could give it a look on that.
I hope to have good news in the next few days.

 

[koalar]

Wouldn’t temporary removing the prop and drive around the block in two wheel drive

Confirm if the noise prop backwards

 

[Herts Hillhopper]

Wouldn’t temporary removing the prop and drive around the block in two wheel drive

Confirm if the noise prop backwards

It’s quite an exercise to remove it though… lots of labour time.

 

[koalar]

It’s quite an exercise to remove it though… lots of labour time.

Official time is 1:15 to drop and replace

Which are always well over the top

So 1/2 an hour would be realistic for a garage on ramps To just drop it

If you can drop it yourself it would save a fair bit in not having diagnosing the problem

 

[koalar]

I bought the centre bearing for a 2005 4x4 then discovered I had no chance of fitting it!

They do all smash apart. You need somewhere solid and a decent size hammer. Not the sort of thing most people have at home.

They are harder to separate than the drive shafts

I have the equipment but if I didn’t I would angle grind the centre outer off. Makes it easier to get a direct hammer blow and take it to an engineering firm/garage to do it for me

It’s not unknown for garages to fail. I posted some pictures of one dismantled which shows where the split is. Which is not obvious.

 

[tomdee]

Wouldn’t temporary removing the prop and drive around the block in two wheel drive

Confirm if the noise prop backwards

The first part I believe it will be out of the question for now. There was no time to do a complete check in order to diagnose the issue. The shop will be closed for holiday in the next three weeks. They will sort it out in September then.
As per the reverse test I must admit I din't tried yet, but I'll do it on wednesday. Again I'm driving the company car and will only have access to panda on wednesday. One other thing I'll do is try do do a video while on the move focusing the middle shaft. I'll try to arrange a smartphone support to fix it underneath the car.
Thank you all for the replies.