Rhythmic knocking / rubbing noise under load – 6R80 Mustang V6 2012

[JarekS]

Hey guys,
I've got a 2012 Mustang V6 (3.7, automatic 6R80) and I'm trying to track down a rhythmic knocking / rubbing noise that happens only under acceleration (load).


Here are the symptoms:

• The sound is most noticeable around 3,000 RPM under moderate throttle.
• The engine itself runs perfectly quiet, even when revved or under load.
• I've checked the U-joints – no play at all.
• Transmission mount and engine mounts are solid.
• The only noticeable play is at the transmission output shaft – when I move the driveshaft up and down, the output seal moves slightly with it.
• The noise sounds like a soft knocking or rubbing, as if two parts were lightly hitting each other in rhythm.
• It's quieter when the transmission is cold, and becomes slightly louder once the fluid warms up.
• Transmission has about 90k miles on it.
• ATF was changed about 2,000 miles ago, fluid is clean and red, with no metal shavings or debris.

The sound seems to come from the middle of the car, around the transmission area, not the rear end.


Has anyone experienced something similar with the output shaft bushing / rear extension housing on the 6R80?
Could that small play cause this kind of rhythmic knock under load?


Any insight would be super helpful - thanks!

 

[Xracer]

Hi Jarek, have you made any progress on this? My Wife's 2012 V6 Auto has what seems to be the same issue. How long have you had the car? Just curious if it's something that started suddenly or if it was like that when you bought it. We bought my Wife's car new and it was perfectly quiet for 6-7 years (about 40k miles - she doesn't drive it much) before I started to notice some general driveline noise coming through the console area. It got worse over the next couple years and has sorta stabilized between 60k miles and now (70k). I've had it to the dealer a couple times and they've declared it "normal for this car", but there's no way it was like this when it was new or we wouldn't have bought it. The sound is a sort of rumbling, clunking sound on acceleration, accompanied by faint whirring sounds of varying pitch that seem to be internal from within the transmission. It basically sounds like there's a hole in the floor under the console, but this is a rust-free, winter-stored car that rarely even sees rain and I've checked the foam gasket that seals the shifter opening and it's intact. I also notice some slop in the output shaft yoke that I've been told is normal. This car is my wife's baby and she planned to keep it forever, but this annoying noise and vibration is starting to make it no-fun anymore.