Hi, I have searched but haven't found anything that seems to fit this issue.

I have a noise coming from somewhere in my Drivetrain. This started last year and was believed to be caused by the driver side front driveshaft due to the damage it sustained when Ihad to remove it from the old wheel bearing. When I went to replace it it led to a series of discoveries that let to me replacing the clutch, flywheel and PTU so these components are all brand new, including hydraulics and most of the bolts.

After all this the clunk was still present but was a lot quieter but after 500 miles it is almost as bad as it was before.

The noise is almost silent on a cold start, I don't really hear it untill the fluids have started to warm so after 2 miles ish. It is not triggered by anything on the road, potholes etc so it is not suspension related and it is not present when stationary so i don't think is an engine/transmission mount.

The noise happens when I am decelerating towards a corner or junction, as my speed drops to around 25mph the drivetrain makes 1 single clonk noise and again when I apply power coming out of the corner. I don't believe it makes the noise on acceleration if the wheels are straight and I believe but can't 100% confirm, that the noise is quieter if the wheels are straight on deceleration.

The noise is still present but sounds a little different if I drive in mud and snow mode, difficult to describe how.

The noise seems to come from everywhere. It usually sounds like it is coming from the front drivers side wheel but sometimes it sounds like it comes from the rear around the diff and occasionally sounds like it is coming from the passenger side wheel. What's interesting to note is the noise only ever happens once per deceleration/acceleration.

I have checked all mounting points of all components and they are tight.

The only thing I have found of note is that the propshaft and Haldex have a few degree's of "Free play" when I rotate them. I don't know if this is normal, but the play is definately on the Haldex end of the prop.

I have a Haldex service kit from Bell and intend to service it this weekend, weather and time permitting.

Can anyone else advise what this might be and if this is a known issue? I have hopefully described this as accurately as I can, it doens't match how others describe the feeling when the Haldex is faulty where they say it feels as if the rear wheels are juddering, unless I am catching this at the very early stages.

Id have suggested engine mounts - but you have tested those.

When you say "decelerating" is that simply taking your foot off the throttle or does it include braking ? If latter Id suggest look at the brakes too.

If you brake whilst coasting in neutral do you get a clonk? Jules

Thanks Jules,

By decelerating I mean slowing down using the engine braking effect after lifting off the throttle. Sometimes the knock happens under braking, sometimes it happens when i dip the clutch to change down to 2nd/3rd, sometimes it happens after I have changed down a gear and am rev matching and litting the clutch again. It seems to be completely random.

I haven't tried to replicate the issue in Neutral. I might give that a try next. I also haven't tried pulling the haldex fuse to disable the AWD system so i might try that too.

Anything that might narrow down the search is worth trying. Jules

Ok so just lifted the car up and had a poke around. Everything I had touched was still tightened up so I didn't leave anything loose thankfully.

The lower rear engine mount is looking a little perished but doesn't seem to have excessive movement but I might just replace it anyway.

The central support for the propshaft caught my eye, the propshaft seems to be sitting at the bottom of the support bush rather than at the center. I don't know if this is normal though.7

there is also a very tiny about of movement between the front and read half of the prop.

The Haldex does have some noticable free play, the input moves a few degree's in either direction and also maybe .5mm up and down so I think an internal bearing may be worn out. Again I don't know if this is normal.

Not had a chance to do any further road tests though.

Hi, did you ever get to the bottom of the problem? I have a similar issue which I suspect is the propshaft, thanks.

I had/still have a similar issue. Cannot pinpoint the cause. Even more - i clearly heard the clunk also when disabling the cruise control at highway speeds, and again when floori g the accrerator pedal. Went with the obvious one - all engine mounts. Although the seemed fine, I still replaced them. Together with this, I also changed the oil in my manual trans, and one of these things improved the situation quite a bit but it was still present. As i had bad splines on my ptu and collar sleeves, this winter i replaced the pto, sleeve, and transmission oil again. Issue seemed to be gone for a while, but i still hear a very distant clunk when agressively changing between first 3 gears.
This issue doesnt lay in alignment, wheels, wishbines, struts, drumsticks, steering rack, dropinks, sway bar, rear subframe, front ptu, rear diff, as i have replaced these all.

And also - the single clunk when stopping comes from your reverse lock out solenoid, i have the same issue.

The best way to test the engine mounts is to put them under load while watching for movement. If it's an auto, it's pretty easy to get a helper to put it in drive or reverse with the brakes on, and watch the resulting movement to see where its occurring. The lower tie bush is visible from the RH wheel arch, with a decent torch.
The upper tie bar is pretty easy to see from the engine bay.

If it's a manual, it's still possible to see movement by slipping the clutch, but don't hold the clutch slipping for too long. Hyundai Ioniq 5 Ultimate. The family car.
2009 Rimini Red SE TD4. Gone.
2006 Tonga Green i6 HSE. Gone.
Audi A5 convertible, my daily driver.
1972 Hillman Avenger GT, the project.

I suggest using an electronic car stethoscope, they are relatively cheap on ebay. I have used one of these kits and found it helped to isolate the location of the noise.

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