General 500X Transmission Noise

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General 500X Transmission Noise

Barry G

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The saga of my 500X clunking transmission goes on ! I have heard from the garage today that the Fiat Technical Guy has visited and not been able to suggest a fix for the clunking that occurs when I put my foot on the accelerator at around 30 - 40 mph. It's a 2 litre auto 4x4 that I bought new in February this year. I think this was the 11th visit having had all the engine/gearbox mounts replaced and 2 new driveshafts they are now suggesting it might be normal !

If you have a 500x the same as mine please could you let me know if yours has a clunking from the transmission, I am concerned that Fiat are going to try and wash their hands of this problem that the simply don't know how to fix.
 
The saga of my 500X clunking transmission goes on ! I have heard from the garage today that the Fiat Technical Guy has visited and not been able to suggest a fix for the clunking that occurs when I put my foot on the accelerator at around 30 - 40 mph. It's a 2 litre auto 4x4 that I bought new in February this year. I think this was the 11th visit having had all the engine/gearbox mounts replaced and 2 new driveshafts they are now suggesting it might be normal !



If you have a 500x the same as mine please could you let me know if yours has a clunking from the transmission, I am concerned that Fiat are going to try and wash their hands of this problem that the simply don't know how to fix.



I believe this same box is used by many other make/models. I cannot vouch for this but found this on a Honda Forum for what it's worth (and no, I don't understand it)

Honda/dealer speak aside and having watched the various youtube videos on how the ZF 9HP transmission operates, the noise might actually make some sense in that the dog clutch operation is performed via hydraulic fluid pressure. What I think may be occurring is kind of like a water hammer phenomena where a valve is being opened/closed quickly to engaged/disengage the dog clutch causing a thud noise in the fluid that reverberates in the car when the valve closes. I guess with the cooler, there is more fluid (marginally I added like 650ml after the install) but there is certainly now external piping much like the water system in your house. This is the most logical explanation I could think of. I am really curious though if anyone without a cooler and the 9spd can hear a thud noise around 28mph and 45mph as the dog clutches operates. Apparently you will really need good ears and be looking for the noise.
 
Hi Barry G.
I also have the 2L auto with 23000 miles and have never experienced what you have described.
So don't let the dealer pull that one out of the hat "they all do that sir" because mine doesn't.
Hope this helps.
Regards
Ed
 
Thanks for that info. The noise doesn't happen at gear changes its when you take your foot off the pedal then put it back on. It happens after coasting uphill, downhill or on the flat, it sounds like there is slack in the drivetrain but was cured for a couple of hundred miles after they changed the driveshafts.
 
I have a 500X Cross Plus 1.4 Turbo MANUAL gearbox.

When I drive with the window down I often hear the "clunk"/"clack" when gear changing.

Over the years manufacturers are chasing the minimal frictions, lower losses, etc. and looser meshing, larger backlash couplings help them to achieve their target. The downside with less tight couplings is increased noise as mating surfaces contact each other.

"Running Clearance" is the key issue here.

Tight running clearance = higher loss = lower change noise = higher MPG
Slack running clearance = lower loss = higher change noise = lower MPG

Getting the balance right is the issue!
 
I have a 500X Cross Plus 1.4 Turbo MANUAL gearbox.

When I drive with the window down I often hear the "clunk"/"clack" when gear changing.

Over the years manufacturers are chasing the minimal frictions, lower losses, etc. and looser meshing, larger backlash couplings help them to achieve their target. The downside with less tight couplings is increased noise as mating surfaces contact each other.

"Running Clearance" is the key issue here.

Tight running clearance = higher loss = lower change noise = higher MPG
Slack running clearance = lower loss = higher change noise = lower MPG

Getting the balance right is the issue!



I get the same with mine.....if a change gear slowly it’s nice and quiet but if I change normally it does clunk a bit but only hear it with window down.....Another Fiat quirk?
 
I get the same with mine.....if a change gear slowly it’s nice and quiet but if I change normally it does clunk a bit but only hear it with window down.....Another Fiat quirk?
Mine is the ZF 9 speed auto so not the same issue I guess. The noise doesn't occur when the car is changing gear it's when you accelerate after coasting. It's been back again today but the expert from Fiat is doing ' they all do that sir ' routine. Funny it didn't do it when I bought it or for a while after they changed the driveshafts. It seems to me that they don't know how to fix it after about six attempts so it's more cost effective to say it's normal. Don't know what to do next as it is so annoying that I don't want to drive it anymore. Will probably end up with a viscous social media campaign (by me!) and a complaint to the motor ombudsman. I don't think I would ever by another Fiat again, which is a pity as I thought my Panda 4x4 was excellent.
 
If this is happening from transitioning from overrun to drive on then this certainly indicates loosely coupled / large running clearance in the final drive, differential, driveshaft couplings.

In overrun the mating surfaces are running on one side and then as power is applied the mating surfaces change side. During the transition the components are free to accelerate through the clearance space till they come to sudden stop on the opposite surfaces.

A good quality oil will always be able to contend with this with regards to wear but sadly the "slap" will generate noise.

As to what is acceptable both in terms of clearances and slap noise is another question.

I'm not familiar with Autobox operation but on a manual box I would:

1) Jack up N/S front wheel clear of ground & handbrake on
2) Select each gear in turn 1,2,3,4,5 & 6
3) Rotate wheel clockwise then counter clockwise till it stops. Note rotational travel. Also apply more speed and force to this and listen to noise
4) Repeat to O/S

On a manual box I think it will be top gear (5 or 6) that will have the most travel and noise, or is it 1st. Can't recall but there will be a difference.

On an Autobox I would *ONLY* attempt the above with the box in PARK. In this case one would not be exercising the gears and I assume only those parts involved (diff & drive shafts?) will be involved.

For my education on a modern autobox (not a Fiat Stilo/Alfa Tiptronic type setup) if you run the engine, shift from PARK to 1st or DRIVE and then turn the engine off does the box remain "in gear"? I suspect also that you can not restart the engine until back in PARK? This would suggest all changes are electrohydraulic unlike older style (80's) boxes where I believe they had a mechanical PARK/release from gear mechanism?
 
I was lookg at this again last night.

http://www.thetruthaboutcars.com/20...-transmission-puts-dog-clutches-on-the-leash/

I think on my car under normal acceleration it changes from 5th to 6th at about 34mph, i expect if i accelerated quicker then it'd hold onto the gear for longer so the speed would be closer to 40mph. I wonder if the issue could be this change from 5th to 6th, or preparation for this change?

Apparently the link above says this is a friction change. does the car behave the same if say you drop from 7th to 5th and then accelerate or just on the way up say from 4th to 6th/7th?

I'm just wondering if the dog clutch is not disengaging fully in the change from 4th to 5th on the way up?

I'd try finding a quiet road and adjust speed to automatically engage 5th/ 6th/ 7th in both directions up and down a few times, these according to the link should all be friction changes and shouldnt involve the dog clutch.

Then maybe try the same in 4th/5th/6th in both directions, these involve the dog clutch activating and deactivating.

And then perhaps try the same in manaul select mode too.

Just guessing here by the way.
 
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