A10 transmission loud mechanical clunk at startup

[Gurney]

Hi,

my A10 transmission is making a loud cluhnk noise at startup (approx 1 second after the engine starts). The mechanical noise is coming from a shock that is felt through the trans and down to the shaft and diff. Sometimes, the car even moves a bit due to this. It's like if a pressure wave put eveything in tension. I attach a video file where you can here the noise.

The thing is, the shock/clunk does not happen at every startup but only when the car was shut down while in Track/Sport mode (or driven in Track/Sport mode for a while and then put back in Normal mode before shut-off).

The trans behaves totally normal in any mode while driving though. The car has 5000km (under warranty). Trans fluid level has been checked at 2000km after breakin period and I have no resaon to believe there's been a leak. I'll bring it to the dealer for them to check but they sell/service so few Mustangs that they would not know the common issues etc

Rings a bell? Any advice?

Thanks

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[bbowes9]

I've had this happen on mine since owning it. Never had any issues with mine. I've seen where others have had It too. That being said yours sounds WAY louder than I've heard and I'd say take it to the dealer because of that.

 

[bbowes9]

This is the other thread about this issue.
https://www.mustang7g.com/forums/threads/singular-knock-on-warm-start.171053/#post-3427949

 

[Gurney]

Thanks for unearthing that thread! Apparently no-one found a solve yet ...

 

[JPGC_S650]

My last GT (2019 GT 10R80) used to do that. It was only every now and again but was concerning when it did. Never had any issues due to it though, I did only put about 50K miles on that car.

 

[Will2]

They all do this I believe. Noticed this on both a '24 Eco and '25 GT. Tends to happen when the car is warm-started, shut off 1-30min ago. Never does this when cold started.

I'm curious what's causing it. Seems troubling, since that mechanical shock can't be good for drivetrain components.

 

[A.alansari]

it is normal took my car to the dealer for this few times they told me it is normal and not worry about it

 

[Zig]

Are you able to verify proper fill / fluid level?

 

[Starship Enterprise]

Mine did that only after I drove it in track mode and/or let the braking be done by the downshifting. People here said something about pressure built up in the trans from aggressive downshifting.

From my understanding, it's normal for this car, and only happens after aggressive driving and is temporary once everything cools down, or the car is driven gently afterward.

 

[Gurney]

Brought the car back to the Ford dealer. They could not find the exact issue and contacted Ford Europe technical service. They could not find the issue either but concluded this loud noise / driveshaft engagement was not normal. They agreed to replace the transmission under warranty.

 

[Xiaoqian]

Brought the car back to the Ford dealer. They could not find the exact issue and contacted Ford Europe technical service. They could not find the issue either but concluded this loud noise / driveshaft engagement was not normal. They agreed to replace the transmission under warranty.

Any updates? Would you let us know if the knock noise stops after replacing the transmission? Thank you!

 

[Gurney]

Any updates? Would you let us know if the knock noise stops after replacing the transmission? Thank you!

So, the dealer changed the A10 transmission under warranty. The trans package included botht the trans, the clutch, the oil pump etc. And the clunk/noise is still there. So it's not a mechanical problem from the trans/clutch. They are investigating:
- A software issue (car sending a wrong command to the trans at startup)
- A play in the downstream shaft, axle, bearings etc (maybe the extra load at startup is normal and something is moving that should not)
- A issue with engine/trans/diff bushings (same as above)

 

[Xiaoqian]

So, the dealer changed the A10 transmission under warranty. The trans package included botht the trans, the clutch, the oil pump etc. And the clunk/noise is still there. So it's not a mechanical problem from the trans/clutch. They are investigating:
- A software issue (car sending a wrong command to the trans at startup)
- A play in the downstream shaft, axle, bearings etc (maybe the extra load at startup is normal and something is moving that should not)
- A issue with engine/trans/diff bushings (same as above)

Thank you for sharing this with us. Hope your dealer can figure out what causes the clunck as soon as they can. Let us know if they find out what's going on.

 

[Cipis]

My trans does the same thing as mentioned when fully warmed up. I figured it is making much lesser clunk in start up if I do following, which helps in my case: After stopping break pedal, Neutral, handbrake, release break pedal, reapply break than to Park, shut off. Before starting I start just ignition without engine (without standing on break) turn off auto stop start, thank crank it up. Maybe try that. Works for me.

 

[Gurney]

Thanks. I will try when I get the car back. It’s still at the Ford dealership now.
for reference and for this interested, here is the clunk shot from beneath and a direct view at the back of the trans.

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