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Discussion Starter #1
I have a 2014 Mustang V6 with a 6 speed manual.
When I drive at any speed, and let off the accelerator, there are times the car will vibrate like it's driving on a rumble strip.
This happens between 30-40 mph in 3rd gear, and 60-70mph in 5th or 6th. What's real confusing is that I can't seem to replicate it on a consistent basis, and it goes away as soon as I start to accelerate again, or depress the clutch.

I did lift the car and checked the driveshaft (2 piece drive shaft), and everything felt solid when trying to rotate it. I have replacement U Joints, but don't want to install them unless i'm sure that's the issue.
Has anyone experience this issue before? Any Suggestions or ideas?

Video for this issue here.


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It sounds like the issue is caused when the momentum of the car is pushing forward on the engine through the driveshaft, if that makes sense. That is why it goes away if you accelerate or disengage the clutch (but does not explain why it does not always happen under those conditions).

That could relate to the driveshaft; it could also relate to a lot of play in the bushing that connects the differential to the upper control arm, or the upper control arm to the car. If there is a lot of play or slop in those bushings, it would allow the differential to rotate back and forth which might cause what you are experiencing. So I'd have a look at those bushings also.

This is just a SWAG (silly wild assed guess) and I really don't know, so hope someone else will chime in with better knowledge!
 

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Is your Clutch slipping at all, it almost sounds like a broken spring in the dual mass flywheel.
 

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I think Jbert is on to it....put the clutch in to see if it continues...if it does, likely driveline issue....IMHO...ujoint/yoke is the 1st thing to look at, if it goes away....time to look at the engine... harmonic balancer may be starting to go "bye-bye"
 

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Just my internet guess, but I do suspect rear upper controller arm, or driveshaft (and associated components) issues myself as well.

If you can get this car on a lift, and replicate SOME of the issue while a helper watches the driveline, it’s possible they may actually be able to observe and pinpoint the issue.

Also, inspect your transmission mount and motor mounts while you’re at it.
 
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Any more information on this?
 

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I have this same issue on my 2013 V6. I posted a thread.
 

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Discussion Starter #9
I was able to replace the driveshaft, however the issue is still there. The only other thing the ford mechanics told me was that it could be the exhaust.

I've noticed it only happens at around 2.5x RPM, and sometimes starts even when I have my foot on the gas. It's much better in the cold, and get's worse as it warms up.
 

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I was able to replace the driveshaft, however the issue is still there. The only other thing the ford mechanics told me was that it could be the exhaust.

I've noticed it only happens at around 2.5x RPM, and sometimes starts even when I have my foot on the gas. It's much better in the cold, and get's worse as it warms up.
Same symptoms with mine. Trans shop replaced right side motor mount because it was a bit worn. They said sound went away with a bit of pressure with floor jack while on hoist. I have drivetrain warranty but clutch not covered so I'm hesitant to let them open it just in case it's not covered. $1700 plus tax quoted for clutch n flywheel. I can't cover that because my job let me go to Covid.
 
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